Audiology : Audiology (from Latin audīre, “to hear”; and from Greek -λογία, -logia) is the branch of science that studies hearing, balance, and related disorders. Its practitioners, who treat those with hearing loss and proactively prevent related damage are audiologists. Employing various testing strategies (e.g. hearing tests otoacoustic emission measurements, videonystagmography, and electrophysiologic tests), audiology aims to determine whether someone can hear within the normal range, and if not, which portions of hearing (high, middle, or low frequencies) are affected and to what degree. If an audiologist determines that a hearing loss or vestibular abnormality is present he or she will provide recommendations to a patient as to what options (e.g. hearing aid, cochlear implants, surgery, appropriate medical referrals) may be of assistance.It is the study of hearing, balance and related disorders.
Audiologists : An audiologist is a health-care professional specializing in identifying, diagnosing, treating and monitoring disorders of the auditory and vestibular system portions of the ear. Audiologists are trained to diagnose, manage and/or treat hearing or balance problems. They dispense hearing aids and recommend and map cochlear implants. They counsel families through a new diagnosis of hearing loss in infants, and help teach coping and compensation skills to late-deafened adults. They also help design and implement personal and industrial hearing safety programs, newborn hearing screening programs, school hearing screening programs, and provide special fitting ear plugs and other hearing protection devices to help prevent hearing loss. In addition, many audiologists work as auditory scientists in a research capacity.
Audiologists have training in anatomy and physiology, hearing aids, cochlear implants, electrophysiology, acoustics, psychophysics, neurology, counseling and sign language. An Audiologist usually graduates with one of the following qualifications ( MSc(Audiology), AuD, PhD, or ScD), depending the program, and country attended.
Amplitude modulation: Immediate processing of signal. Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent. For example, changes in signal strength may be used to specify the sounds to be reproduced by a loudspeaker, or the light intensity of television pixels. Contrast this with frequency modulation, in which the frequency is varied, and phase modulation, in which the phase is varied.
In the mid-1870s, a form of amplitude modulation—initially called “undulatory currents”—was the first method to successfully produce quality audio over telephone lines. Beginning with Reginald Fessenden’s audio demonstrations in 1906, it was also the original method used for audio radio transmissions, and remains in use today by many forms of communication—”AM” is often used to refer to the mediumwave broadcast band.
Auto scope Adaptive Directionality: This is for providing speech clarity in any listening situation
Acoustic Neuroma – A vestibular schwannoma, often called an acoustic neuroma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve (CN VIII). The term “vestibular schwannoma” involves the vestibular portion of the 8th cranial nerve and arises from Schwann cells, which are responsible for the myelin sheath in the peripheral nervous system. Approximately 3,000 cases are diagnosed each year in the United States with a prevalence of about 1 in 100,000 worldwide. It comprises 5-10% of all intracranial neoplasms in adults. Incidence peaks in the fifth and sixth decades and both sexes are affected equally. A tumor, usually benign, which develops on the hearing and balance nerves and can cause gradual hearing loss, tinnitus, and dizziness.
Acquired deafness: The loss of hearing that occurs or develops some time during a person’s life but was not present at birth.
Acquired deafness contrasts to congenital deafness which is present at birth.
The distinction between acquired and congenital deafness specifies only the time that the deafness appears. It does not specify whether the cause of the deafness is genetic (inherited).
Acquired deafness may or may not be genetic. For example, it may be a manifestation of a delayed-onset form of genetic deafness. Or acquired deafness may be due to damage to the ear from noise.
Congenital deafness similarly may or may not be genetic. For example, it may be associated with a white forelock and be caused by a genetic disease called Waardenburg syndrome. Or congenital deafness may be due to something such as the rubella virus to which the mother was exposed during pregnancy.
– Loss of hearing that occurs or develops sometime in the course of a lifetime, but is not present at birth.
American Sign Language (ASL) – Manual (sign) language with its own syntax and grammar used primarily by people who are deaf. American Sign Language (ASL) is a sign language, a language in which the hands, arms, head, facial expression and body language are used to speak without sound. ASL is not related to English, and features an entirely different grammar and vocabulary. In the 1960s, ASL was sometimes referred to as “Ameslan” but this term is now obsolete.
ASL is the predominant sign language of deaf communities in the United States and English-speaking parts of Canada. Although the United Kingdom and the United States / Canada share English as a common oral and written language, British Sign Language (BSL) is a completely different language from ASL, and they are not mutually intelligible. ASL is instead related to French Sign Language.
Besides North America, dialects of ASL or ASL-based creoles are used.
Assistive Devices – Tools and devices such as alarms, alerting devices, or FM systems used to help people hear to perform daily actions, tasks, and activities. Learn more about assistive listening devices. Assistive technology or adaptive technology (AT) is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them. AT promotes greater independence by enabling people to perform tasks that they were formerly unable to accomplish, or had great difficulty accomplishing, by providing enhancements to, or changing methods of interacting with, the technology needed to accomplish such tasks.
The terms may be used with a slight difference in meaning. “Assistive technology” may specifically refer to new devices designed to assist with tasks. “Adaptive technology” may specifically mean making modifications to existing devices and technology to enable their use by people with disabilities. Both terms refer to the goal of accommodating people with disabilities, who otherwise would be prevented from completing tasks.
Examples of Assistive technology include the curb cut in architecture, standing frames, text telephones, accessible keyboards, large print, Braille, and speech recognition software. Assistive technology or interventions are sometimes controversial or rejected, for example in the controversy over cochlear implants for children.
Universally accessible technology yields great rewards to the typical user as well; good accessible design is universal design. One example is the “curb cuts” (or dropped curbs) in the sidewalk at street crossings. While these curb cuts enable pedestrians with mobility impairments to cross the street, they also aid parents with carriages and strollers, shoppers with carts, and travelers and workers with pull-type bags.
Audiologist – A health care professional trained to evaluate hearing loss and related disorders, including balance (vestibular) disorders and tinnitus, and to rehabilitate people with hearing loss and related disorders. Audiologists use a variety of tests and procedures to assess hearing and balance function and to fit and dispense hearing aids and other assistive devices for hearing loss. Most audiologists have advanced doctorate degrees.
Auditory Brainstem Response (ABR) Test – Used to test the hearing of infants and young children, or to test the functioning of the hearing nerve. This painless procedure involves attaching recording disks to the head to record electrical activity from the hearing nerve and brain stem.
Auditory Nerve – Eighth cranial nerve that connects the inner ear to the brain.Auditory Perception – Ability to identify, interpret , and attach meaning to sound.
Auditory Processing Disorder (APD) – Inability of an individual with normal hearing and intelligence to differentiate, recognize, or understand sounds normally. Auditory Processing Disorder (APD), also known as Central Auditory Processing Disorder (CAPD) is an umbrella term for a variety of disorders that affect the way the brain processes auditory information. Individuals with APD usually have normal structure and function of the outer, middle and inner ear (peripheral hearing). However, they cannot process the information they hear in the same way as others do, which leads to difficulties in recognizing and interpreting sounds, especially the sounds composing speech. It is thought that these difficulties arise from dysfunction in the central nervous system (i.e., brain).
APD does not feature in mainstream diagnostic classifications such as the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). APD is not a coherent syndrome with clear diagnostic criteria. Rather, it is a label applied when a person has difficulties in recognizing and interpreting sounds that are not due to peripheral hearing loss.
APD can affect both children and adults, although the actual prevalence is currently unknown. It has been suggested that males are twice as likely to be affected by the disorder than females, but there are no good epidemiological studies.
Autoimmune Hearing Loss – Hearing loss when one’s immune system produces abnormal antibodies that react against the body’s healthy tissues. May be associated with tissue-causing disease, such as rheumatoid arthritis or lupus. Autoimmune inner ear disease is a suspected autoimmune disease characterized by rapidly progressive bilateral sensorineural hearing loss. It occurs when the body’s immune system attacks cells in the inner ear that are mistaken for a virus or bacteria. Autoimmune inner ear disease was first described by Dr. Brian McCabe of the University of Iowa in 1979. AIED is generally caused by either antibodies or immune cells that cause damage to the inner ear. There are several autoimmune disorders to which AIED is related:
- Bystander damage
- Genetic factors
- Drug Use (opiate-based painkillers like OxyConti)
Research has found that long term abuse of opiate-based painkillers (such as OxyContin and Hydrocodone) can lead to profound hearing loss caused by damage to the inner ear, according to Dr. Gail Ishiyama, an assistant professor at the UCLA department of neurology.
Adaptive directional microphones – directional microphone system which, when activated, can adapt based on the location of the noise. Directional microphones vary the direction of maximum amplification. The direction of amplification is varied by the hearing aid processor. The processor attempts to provide maximum amplification in the direction of the speech signal. Unless the user manually temporarily switches to a “restaurant program, forward only mode” adaptive directional microphones have a disadvantage of amplifying speech of other talkers in a restaurant. This makes it difficult for the processor to select the desired speech signal. Another disadvantage is that noise often mimics speech characteristics, making it difficult to separate the speech from the noise. Despite the disadvantages, adaptive directional microphones can provide improved speech recognition in noise.
Directional microphones only provide benefit when the distance to the talker is small. In contrast, an FM system continues to provide a better signal to noise ratio even at larger speaker to talker distances.
Adaptive feedback cancellation – a digital process which creates a filter within the amplifier of the hearing aid to cancel feedback the moment it is detected without reducing or altering the hearing aid’s response. The filter will automatically change (or adapt) if the feedback is caused by a different or changing situation. Adaptive feedback cancellation is a common method of cancelling audio feedback in a variety of electro-acoustic systems such as digital hearing aids. The time varying acoustic feedback leakage paths can only be eliminated with adaptive feedback cancellation. When an electro-acoustic system with an adaptive feedback canceller is presented with a correlated input signal, a recurrent distortion artifact, entrainment is generated. There is a difference between the system identification and feedback cancellation.
Adaptive feedback cancellation has its application in echo cancellation. The error between the desired and the actual output is taken and given as feedback to the adaptive processor for adjusting its coefficients to minimize the error.
In hearing aids, feedback arises when a part of the receiver (loudspeaker) signal is captured by the hearing aid microphone(s), gets amplified in the device and starts to loop around through the system. When feedback occurs, it results in a disturbingly loud tonal signal. Feedback is more likely to occur when the hearing aid volume is increased, when the hearing aid fitting is not in its proper position or when the hearing aid is brought close to a reflecting surface (e.g. when using a mobile phone). Adaptive feedback cancellation algorithms are techniques that estimate the transmission path between loudspeaker and microphone(s). This estimate is then used to implement a neutralizing electronic feedback path that suppresses the tonal feedback signal.
Automatic Signal processing (ASP)/Automatic Gain Control (AGC)-Input – an acronym for the Automatic Signal Processing / Automatic Gain Control-Output. This circuit automatically reduces the volume of a hearing aid in response to sound which has exceeded a certain level. With the ASP/AGC-Output circuit, loud sounds are reduced after the amplifier.
Automatic Signal processing/ASP (Bass Increase at Low Level Circuitry) – stands for the Automatic Signal Processing Bass Increases at Low Levels. This circuit also decreases the bass at high levels. BILL circuitry is often marketed under the trademark name “Manhattan” circuit. BILL circuitry is intended for wearers who frequently find themselves in noisy environments, especially environments where low frequency noise is a constant factor. Harsh or shrill sounds are not amplified, but are actually reduced by this circuit.
Automatic Signal Processing/ASP (Programmable Increase at Low Level Circuitry) – stands for Automatic Signal Processing Programmable Increases at Lower Levels. This type of circuitry is more versatile than TILL or BILL circuitry because it can be programmed by computer to automatically perform as a BILL circuit on one channel and a TILL circuit on another. The user can switch between circuits as listening environments change.
ASP (Treble Increase at Low Level/TILL Circuitry) – stands for the Automatic Signal Processing Treble Increase at Low Levels. This circuit also decreases the high frequency column at high levels. TILL circuitry is often marketed under the trademark name “K-AMP.” TILL circuitry is intended for wearers who need more volume to hear the quiet sounds than they do for loud sounds. Harsh or shrill sounds are not amplified, but pass through the circuit unaltered.
Audiogram – An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels and the X axis represents frequency measured in Hertz. Most audiograms cover a limited range of frequencies 100 Hz to 8000 Hz (8 kHz) because this range includes the fundamental frequency of sounds in speech. The threshold of hearing is plotted relative to a standardised curve that represents ‘normal’ hearing, in dB(HL). They are not the same as equal-loudness contours, which are a set of curves representing equal loudness at different levels, as well as at the threshold of hearing, in absolute terms measured in dB SPL (sound pressure level).
Audiograms are set out with frequency in hertz (Hz) on the horizontal axis, most commonly on a logarithmic scale, and a linear dBHL scale on the vertical axis. Normal hearing is classified as being between −10 dB(HL) and 15 dB(HL, although 0 dB from 250 Hz to 8 kHz is deemed to be ‘average’ normal hearing.
Hearing thresholds of humans and other mammals can be found by using behavioural hearing tests or physiological tests. An audiogram can be obtained using a behavioural hearing test called Audiometry. For humans the test involves different tones being presented at a specific frequency (pitch) and intensity (loudness). When the person hears the sound they raise their hand or press a button so that the tester knows that they have heard it. The lowest intensity sound they can hear is recorded. The test varies for children, their response to the sound can be a head turn or using a toy. The child learns what they can do when they hear the sound, for example they are taught that when they heard the sound they can put a toy man in a boat. A similar technique can be used when testing some animals but instead of a toy, food can be used as a reward for responding to the sound. Physiological tests do not need the patient to respond (Katz 2002). For example when performing the brainstem auditory evoked potentials the patient’s brainstem responses are being measured when a sound is played into their ear. How often hearing should be tested depends mainly on noise exposure. People who are regularly exposed to hazardous noise should have their hearing tested once a year. People with healthy hearing and who are not exposed to much noise should have their hearing tested once every three years
a graph on which to record the auditory threshold by frequency of a patient’s hearing.
Audiometry – the measurement of hearing.
Aural – having to do with the ear or hearing.
Audiotry nerve – connects the inner ear and the brain; serves in hearing and balance.
Automatic directional microphones – directional microphone technology that is automatically engaged or disengaged without user direction.
Automatic signal processing (ASP)- the family of hearing aid circuits which automatically change the gain (volume) and frequency response (tones such as bass, midrange and treble) as a function of the sound entering the hearing aid microphone.
Aphasia – Total or partial loss of the ability to use or understand language—usually caused by stroke, brain disease, or injury. Aphasia ( /əˈfeɪʒə/ or /əˈfeɪziə/, from ancient Greekἀφασία (ἄφατος, ἀ- + φημί), “speechlessness”) is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write.
Acute aphasia disorders usually develop quickly as a result of head injury or stroke, and progressive forms of aphasia develop slowly from a brain tumor, infection, or dementia. The area and extent of brain damage or atrophy will determine the type of aphasia and its symptoms. Aphasia types include expressive aphasia, receptive aphasia, conduction aphasia, anomic aphasia global aphasia, primary progressive aphasias and many others (see Category:Aphasias. Medical evaluations for the disorder range from clinical screenings by a neurologist to extensive tests by a Speech-Language Pathologist.
Most acute aphasia patients can recover some or most skills by working with a Speech-Language Pathologist. This rehabilitation can take two or more years and is most effective when begun quickly. Only a small minority will recover without therapy, such as those suffering a ministroke. Improvement varies widely, depending on the aphasia’s cause, type, and severity. Recovery also depends on the patient’s age, health, motivation, handedness, and educational level.
Aphonia – Complete loss of voice. Aphonia is the inability to speak. It is considered more severe than dysphonia. A primary cause of aphonia is bilateral disruption of the recurrent laryngeal nerve, which supplies nearly all the muscles in the larynx. Damage to the nerve may be the result of surgery (e.g., thyroidectomy) or a tumor. Psychogenic aphonia
Psychogenic aphonia is often seen in patients with underlying psychological problems. Laryngeal examination will show usually bowed vocal folds that fail to adduct to the midline during phonation. However, the vocal folds will adduct when the patient is asked to cough. Treatment should involve consultation and counseling with a speech pathologist and, if necessary, a psychologist.
In this case, the patient’s history and the observed unilateral immobility rules out functional aphonia. There are many reasons why this may happen. Injuries seem to be the cause of aphonia rather frequently; minor injuries can affect the second and third dorsal area in such a manner that the lymph patches concerned with coordination become either atrophic or relatively nonfunctioning. Tracheotomy can also cause aphonia.
Basically, any injury or condition that prevents the vocal cords, the paired bands of muscle tissue positioned over the trachea, from coming together and vibrating will have the potential to make a person unable to speak. When a person prepares to speak, the vocal folds come together over the trachea and vibrate due to the airflow from the lungs. This mechanism produces the sound of the voice. If the vocal folds cannot meet together to vibrate, sound will not be produced. Aphonia can also be caused by and is often accompanied by fear. Aphonia means “no sound.” In other words, a person with this disorder has lost his/her voice.
Apraxia – Inability to execute a voluntary movement despite being able to demonstrate normal muscle function post stroke. Apraxia (from the Greek root word praxis, for an act, work, or deed, preceded by an privative a, meaning without.) is characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements. It is a disorder of motor planning, which may be acquired or developmental, but is not caused by incoordination, sensory loss, or failure to comprehend simple commands (which can be tested by asking the person to recognize the correct movement from a series). It is caused by damage to specific areas of the cerebrum. Apraxia should not be confused with ataxia, a lack of coordination of movements; aphasia, an inability to produce and/or comprehend language; abulia, the lack of desire to carry out an action; or allochiria, in which patients perceive stimuli to one side of the body as occurring on the other. There are several types of apraxia including:
- Ideomotor Apraxia: These patients have deficits in their ability to plan or complete motor actions that rely on semantic memory. They are able to explain how to perform an action, but unable to “imagine” or act out a movement such as “pretend to brush your teeth” or “pucker as though you bit into a sour lemon.” The ability to perform an action automatically when cued; however, remains intact. This is known as automatic-voluntary dissociation. For example they may not be able to pick up a phone when asked to do so, but can perform the action without thinking when the phone rings.
- Ideational/Conceptual Apraxia: Patients have an inability to conceptualize a task and impaired ability to complete multistep actions. Consists of an inability to select and carry out an appropriate motor program. For example, the patient may complete actions in incorrect orders, such as buttering bread before putting it in the toaster, or putting on shoes before putting on socks. There is also a loss of ability to voluntarily perform a learned task when given the necessary objects or tools. For instance, if given a screwdriver, the patient may try to write with it as if it were a pen, or try to comb one’s hair with a toothbrush.
- Buccofacial or orofacial apraxia: Non-verbal oral or buccofacial ideomotor apraxia resulting in difficulty carrying out movements of the face on demand. For example, an inability to lick one’s lips or whistle.
- Constructional apraxia: The inability to draw or construct simple configurations, such as intersecting pentagons.
- Gait apraxia
- Limb-kinetic apraxia: Difficulty making precise movements with an arm or leg.
- Oculomotor apraxia: Difficulty moving the eye, especially with saccade movements that direct the gaze to targets. This is one of the 3 major components of Balint’s syndrome.
- Apraxia of speech: Difficulty planning and coordinating the movements necessary for speech.
Each type may be tested at decreasing levels of complexity; if the person tested fails to execute the commands, you can make the movement yourself and ask that the person mimic it, or you can even give them a real object (like a toothbrush) and ask them to use it.
Verbal apraxia of speech
Apraxia may be accompanied by a language disorder called aphasia. Because this is such a frequently encountered type of apraxia, an entire section is devoted to it:
Symptoms of Acquired Apraxia of speech (AOS) and Childhood Apraxia of Speech (CAS) include inconsistent articulatory errors, groping oral movements to locate the correct articulatory position, and increasing errors with increasing word and phrase length. AOS often co-occurs with Oral Apraxia (during both speech and non-speech movements) and Limb Apraxia.
Childhood Apraxia of Speech (CAS) presents in children who have no evidence of difficulty with strength or range of motion of the articulators, but are unable to execute speech movements because of motor planning and coordination problems. This is not to be confused with phonological impairments in children with normal coordination of the articulators during speech.
Acquired apraxia of speech involves the loss of previously acquired speech levels. It occurs in both children and adults who have (prior to the onset of apraxia) acquired some level of speaking ability. Unlike Childhood Apraxia of Speech, AOS is typically the result of a stroke, tumor, or other known neurological illness or injury.Apraxia is most often due to a lesion in the left hemisphere, and is typically in the parietal lobe and frontal lobe; however lesions in other brain areas, including the right hemisphere, due to stroke, ABI, or neurodegenerative diseases can result in apraxia.
Due to the common left parietal and frontal lobe locations, apraxia is often accompanied by aphasia which can make diagnosis challenging as it is difficult to tell if the patient’s motor impairments are due to apraxia or from the decreased language comprehension associated with aphasia.
Ideational apraxia is commonly associated with confusion states and dementia.
Constructional apraxia is associated with hepatic encephalopathy due to cerebral edema. Although qualitative and quantitative studies exist, there is little consensus on the proper method to assess for apraxia. The criticisms of past methods include failure to meet standard psychometric properties as well as research-specific designs that translate poorly to non-research use.
The Test to Measure Upper Limb Apraxia (TULIA) is one method of determining upper limb apraxia through the qualitative and quantitative assessment of gesture production. In contrast to previous publications on apraxic assessment, the reliability and validity of TULIA was thoroughly investigated. The TULIA consists of subtests for the imitation and pantomime of non-symbolic (“put your index finger on top of your nose”), intransitive (“wave goodbye”) and transitive (“show me how to use a hammer”) gestures. Discrimination (differentiating between well- and poorly-performed tasks) and recognition (indicating which object corresponds to a pantomimed gesture) tasks are also often tested for a full apraxia evaluation.
However, there may not be a strong correlation between formal test results and actual performance in everyday functioning or activities of daily living (ADL). A comprehensive assessment of apraxia should include formal testing, standardized measurements of ADLs, observation of daily routines, self-report questionnaires and targeted interviews with the patients and their relatives.Recommended treatment for individuals with apraxia includes physical therapy, occupational therapy, play therapy, music therapy, and/or speech therapy.[Yet, treatments for apraxia have received little attention for several reasons, including the tendency for the condition to resolve spontaneously in acute cases. Additionally, the very nature of the automatic-voluntary dissociation of motor abilities that defines apraxia means that patients may still be able to automatically perform activities if cued to do so in daily life. Nevertheless, research shows that patients experiencing apraxia have less functional independence in their daily lives, and that evidence for the treatment of apraxia is scarce. However, a literature review of apraxia treatment to date reveals that although the field is in its early stages of treatment design, certain aspects can be included to treat apraxia. One method is through rehabilitative treatment, which has been found to positively impact apraxia, as well as activities of daily living. In this review, rehabilitative treatment consisted of 12 different contextual cues, which were used in order to teach patients how to produce the same gesture under different contextual situations. Additional studies have also recommended varying forms of gesture therapy, whereby the patient is instructed to make gestures (either using objects or symbolically meaningful and non-meaningful gestures) with progressively less cuing from the therapist. Thus, gesture therapy has been found to be the most effective treatment for apraxia at the current time. While other modes of therapy, including direct, exploratory, and strategy training hold promise, there is insufficient evidence of their efficacy. The prognosis for individuals with apraxia varies. With therapy, some patients improve significantly, while others may show very little improvement. Some individuals with apraxia may benefit from the use of a communication aid. However, many people with apraxia are no longer able to be independent. They should avoid activities in which they might injure themselves or others.
Occupational therapy and counseling and play therapy may help both patients and their caregivers learn ways to deal with the apraxia. However, because people with limb apraxia may have trouble directing their motor movements, occupational therapy for stroke or other brain injury can be difficult.
No drug has been shown useful for treating apraxia.
Articulation Disorder – Inability to correctly produce speech sounds (phonemes) because of imprecise placement, timing, pressure, speed, or flow of movement of the lips, tongue, or throat. Speech sound disorders are speech disorders in which some speech sounds (called phonemes) in a child’s (or, sometimes, an adult’s) native language are either not produced, not produced correctly, or are not used correctly. Errors produced by children with speech sound disorders are typically classified into four categories:
- Omissions: Certain sounds are not produced — entire syllables or classes of sounds may be deleted; e.g., fi’ for fish or ‘at for cat.
- Additions (or Commissions): an extra sound or sounds are added to the intended word.
- Distortions: Sounds are changed slightly so that the intended sound may be recognized but sound “wrong,” or may not sound like any sound in the language. The best known example of a distortion is the lisp.
- Substitutions: One or more sounds are substituted for another; e.g., wabbit for rabbit or tow for cow.
Sometimes, even for experts, telling exactly which type has been made is not obvious — some distorted forms of /r/ may be mistaken for /w/ by a casual observer, yet may not actually be either sound but somewhere in between. Further, children with severe speech sound disorders may be difficult to understand, making it hard to tell what word was actually intended and thus what is actually wrong with it.
There are three different levels of classification when determining the magnitude and type of an error that is produced:
- Sounds the patient can produce
- A: Phonemic- can be produced easily; used meaningfully and contrastively
- B: Phonetic- produced only upon request; not used consistently, meaningfully, or contrastively; not used in connected speech.
- Stimulable sounds
- A: Easily stimulable
- B: Stimulable after demonstration and probing (i.e. with a tongue depressor).
- Cannot produce the sound .
- A: Cannot be produced voluntarily.
- B: No production ever observed.
Note, that omissions do not mean the sound cannot be produced, and some sounds may be produced for easily of frequently when appearing with certain other sounds: someone might be able to say “s” and “t” separately, but not “st,” or may be able to produce a sound at the beginning of a word but not at the end. The magnitude of the problem will often vary between different sounds from the same speaker.
Speech sound disorders may be subdivided into two primary types, articulation disorders (also called phonetic disorders) and phonemic disorders (also called phonological disorders). However, some may have a mixed disorder in which both articulation and phonological problems exist. Though speech sound disorders are associated with childhood, some residual errors may persist into adulthood.
Articulation disorders (also called phonetic disorders, or simply “artic disorders” for short) are based on difficulty learning to physically produce the intended phonemes. Articulation disorders have to do with the main articulators which are the lips, teeth, alveolar ridge, hard palate, velum, glottis, and the tongue. If the disorder has anything to do with any of these articulators, then it’s an articulation disorder. There are usually fewer errors than with a phonemic disorder, and distortions are more likely (though any omissions, additions, and substitutions may also be present). They are often treated by teaching the child how to physically produce the sound and having them practice its production until it (hopefully) becomes natural. Articulation disorders should not be confused with motor speech disorders, such as Dysarthria (in which there is actual paralysis of the speech musculature) or Childhood Apraxia of Speech (in which motor planning is severely impaired).
In a phonemic disorder (also called a phonological disorders) the child is having trouble learning the sound system of the language, failing to recognize which sounds contrasts contrast meaning. For example, the sounds /k/ and /t/ may not be recognized as having different meanings, so “call” and “tall” might be treated as homophones, both being pronounced as “tall.” This is called phoneme collapse, and in some cases many sounds may all be represented by one — e.g., /d/ might replace /t/, /k/, and /g/. As a result, the number of error sounds is often (though not always) greater than with articulation disorders and substitutions are usually the most common error. Phonemic disorders are often treated using minimal pairs (two words that differ by only one sound) to draw the child’s attention to the difference and its effect on communication.
Some children with phonemic disorders may seem to be able to hear phoneme distinctions in the speech of others but not their own. This is called the fis phenomenon based on scenario in which a speech pathologist will say, “Did you say ‘fis,’ don’t you mean ‘fish’?” To which the child responds, “No, I didn’t say ‘fis,’ I said ‘fis’.” In some cases, the sounds produced by the child are actually acoustically different, but not significantly enough for others to distinguish – ironically, because those sounds are not phonemically unique to speakers of the language.
Though phonemic disorders are often considered language disorders in that it is the language system that is affected, they are also speech sound disorders in that the errors relate to use of phonemes. This makes them different from Specific Language Impairment (SLI), which is primarily a disorder of the syntax (grammar) and usage of language rather than the sound system. However, the two can coexist, affecting the same person.
Other disorders can deal with a variety of different ways to pronounce consonants. Some examples are glides and liquids. Glides occur when the articulatory posture changes gradually from consonant to vowel. Liquids can include /l/ and /.1/ (-Alex Restrepo).
Mixed Speech Sound Disorders
In some cases phonetic and phonemic errors may coexist in the same person. In such case the primary focus is usually on the phonological component but articulation therapy may be needed as part of the process, since teaching a child how to use a sound is not practical if the child doesn’t know how to produce it.
Even though most speech sound disorders can be successfully treated in childhood, and a few may even outgrow them on their own, errors may sometimes persist into adulthood. Such persisting errors are referred to as “residual errors” and may remain for life.
Most speech sound disorders occur without a known cause. A child may not learn how to produce sounds correctly or may not learn the rules of speech sounds on his or her own. These children may have a problem with speech development, which does not always mean that they will simply outgrow it by themselves. Many children do develop speech sounds over time but those who do not often need the services of a Speech-Language Pathologist to learn correct speech sounds.
Some speech sound errors can result from physical problems, such as:
Genetic syndrome(e.g Down Syndrome).
Cleft palete or other physical anamolies of the mouth.
Neurological Disorders.(e.g cerebral palsy)
Assistive Devices – Tools and devices such as alphabet boards, text telephones, or text-to-speech conversion software used to help people with communication disorders perform actions, tasks, and activities. Assistive technology or adaptive technology (AT) is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them. AT promotes greater independence by enabling people to perform tasks that they were formerly unable to accomplish, or had great difficulty accomplishing, by providing enhancements to, or changing methods of interacting with, the technology needed to accomplish such tasks.
The terms may be used with a slight difference in meaning. “Assistive technology” may specifically refer to new devices designed to assist with tasks. “Adaptive technology” may specifically mean making modifications to existing devices and technology to enable their use by people with disabilities. Both terms refer to the goal of accommodating people with disabilities, who otherwise would be prevented from completing tasks.
Examples of Assistive technology include the curb cut in architecture, standing frames, text telephones, accessible keyboards, large print, Braille, and speech recognition software. Assistive technology or interventions are sometimes controversial or rejected, for example in the controversy over cochlear implants for children.
Universally accessible technology yields great rewards to the typical user as well; good accessible design is universal design. One example is the “curb cut” (or dropped curbs) in the sidewalk at street crossings. While these curb cuts enable pedestrians with mobility impairments to cross the street, they also aid parents with carriages and strollers, shoppers with carts, and travelers and workers with pull-type bags.
Augmentative Devices – Tools that help individuals with limited or absent speech to communicate. These include communication boards, pictographs (symbols that look like the things they represent), or ideographs (symbols representing ideas). Augmentative and alternative communication .
An AAC user uses number coding on an eye gaze communication board.
Augmentative and alternative communication (AAC) is an umbrella term that encompasses methods of communication for those with impairments or restrictions on the production or comprehension of spoken or written language. AAC systems are extremely diverse and depend on the capabilities of the user. They may be as basic as pictures on a board that the are used to request food, drink, or other care; or they can be advanced speech generating devices, based on speech synthesis, that are capable of storing hundreds of phrases and words.
Modern use of AAC began in the 1950s with systems for users who had lost the use of speech following surgical procedures During the 1960s the use of manual sign language grew greatly, but it was not until the 1980s that AAC began to emerge as an area in its own right. AAC is now used for a wide variety of speech impairments. Studies show that AAC use does not impede the development of speech, and may even result in a modest increase in speech production.
A great diversity of diagnoses, including cerebral palsy, intellectual impairment, autism, and many others, cover varying degrees of communication impairment. AAC interventions are highly individualized, taking into account specific abilities of language comprehension, social-relational characteristics, learning strengths and weaknesses, and developmental patterns for specific types of intellectual disabilities. AAC can be used to aid both spoken and written language, and can supplement or replace speech and writing as necessary. AAC can be a permanent addition to a person’s communication or a temporary aid. The systems used in AAC include gestures, hand signals, photographs, pictures, line drawings, words and letters, which can be used alone or in combination to communicate.
Aided AAC makes great use of symbols, particularly for non-literate users, as well as a large variety of input methods. The specific access method will depend on the skills and abilities of the user. Body parts, pointers, adapted mice, joysticks, or eye tracking could be used, whereas switch access scanning is often used for indirect selection. In many cases, rate enhancements methods may be used to speed up the generation of messages. Clearly, an evaluation of a user’s abilities and requirements is necessary to match a user with the most appropriate AAC method, input approach, and vocabulary. This evaluation requires the input of family, particularly for early intervention. Respecting ethnicity and family beliefs are key to a family-centered and ethnically competent approach.Adult AAC users generally have satisfying relationships with family and friends and engage in pleasurable and interesting life activities.
Deafness and hearing loss
A sign in a train station indicates a Hearing induction loop is available for travellers to hear public address system messages transmitted directly to their hearing aid receiver.
- Fire alarm paging system
- Loop system (portable and fixed)
- Radio aids
- Telecommunications device for the deaf
- Video cassette recorders that can read and record subtitles (Closed Captioning).
- Vibrating fire alarm placed under pillow when asleep.
- Door bell lighting system.
Assistive Technology for Cognition
Assistive Technology for Cognition (ATC) is the use of technology (usually high tech) to augment and assistive cognitive processes such as attention, memory, self-regulation, navigation, emotion recognition and management, planning, and sequencing activity. Systematic reviews of the field have found that the number of ATC are growing rapidly, but have focused on memory and planning, that there is emerging evidence for efficacy, that a lot of scope exists to develop new ATC. Examples of ATC include:
- NeuroPage uses a pager system to prompt users about meetings. It was one of the earliest ATC to provide randomised control trial evidence of efficacy
- Wakamaru provides companionship, reminds users to take medicine and calls for help if something is wrong.
- Telephone Reassurance: community based program that calls seniors at home ensuring their well-being.
- Cosmobot is part of a play therapy system designed to motivate children to participate in therapy.
- General User Interface for Disorders of Execution (GUIDE) is an interactive verbal prompting system that talks people with cognitive impairment through daily routine tasks.
Upper Extremity Prosthesis
There are many variations of upper extremity prosthesis. Prosthetics are constantly progressing as technology improves. The most commonly used terminal device is a moveable or non-moveable hand. Compared to other devices, this is a more simplistic and cheap alternative. The four large categories that cover upper body prosthetics are the following: body powered, Myoelectric, and targeted muscle reinnervation.
Body powered prosthetics use a system of nonelastic straps for harnesses and control. This device requires minimal physical exertion. These “Terminal Devices” are not the most aesthetically pleasing, but they are simple and cheap.
Myoelectric arms read and respond to electrical pulses created by remaining arm muscles. They are less economical than body powered prosthetics, but they are far more sophisticated. Myoelectric arms generally rely on a surgery called TMR (Targeted Muscle Reinnervation). This procedure moves residual nerves from amputated limbs into unused muscle regions. (Velez) Myoelectric prosthetics use electrodes that are placed on top of the rerouted nerves.
Luke DEKA Arm
A large majority of patients with prosthetics wind up not using their devices. There are many reasons including discomfort and functionality. A new upper arm prosthetic created by DEKA and supported by DARPA (Defense Advanced Research Projects Agency) aims to create a new all around better device. This device, nicknamed “Luke” after the Jedi knight in Star Wars, is far more advanced than any other device currently on the market. It boasts 10 degrees of motion and features moving fingers, wrist, elbow, and shoulder, all powered by electric motors. The arm can be operated two different ways: by a controller operated by the foot, or myoelectrically, using electrical pulses sent through remaining muscles. The hand of “Luke” contains various sensors that enable the user to do a multitude of tasks that the average person takes for granted; the hand can pick up a grape without squishing it, install a light bulb with ease, and it can even manipulate chopsticks. One important feature of the arm is that it weighs between 8 and 12 pounds, equivalent to the weight of a female arm. This means that the device should feel more natural to the operator and will also be far more comfortable.
Aural Rehabilitation – Techniques used with people who are hearing impaired to improve their ability to speak and communicate.
Autism – A brain disorder that begins in early childhood and persists throughout adulthood; affects three crucial areas of development: communication, social interaction, and creative or imaginative play. Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. The diagnostic criteria require that symptoms become apparent before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their synapses connect and organize; how this occurs is not well understood It is one of three recognized disorders in the autism spectrum (ASDs), the other two being Asperger syndrome, which lacks delays in cognitive development and language, and pervasive developmental disorder, not otherwise specified (commonly abbreviated as PDD-NOS), which is diagnosed when the full set of criteria for autism or Asperger syndrome are not met.
Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether ASD is explained more by rare mutations, or by rare combinations of common genetic variants. In rare cases, autism is strongly associated with agents that cause birth defects. Controversies surround other proposed environmental causes, such as heavy metals, pesticides or childhood vaccines; the vaccine hypotheses are biologically implausible and lack convincing scientific evidence. The prevalence of autism is about 1–2 per 1,000 people worldwide, and the Centers for Disease Control and Prevention (CDC) report 11 per 1,000 children in the United States are diagnosed with ASD as of 2008. The number of people diagnosed with autism has increased dramatically since the 1980s, partly due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved.
Parents usually notice signs in the first two years of their child’s life. The signs usually develop gradually, but some autistic children first develop more normally and then or cognitive intervention can help autistic children gain self-care, social, and communication skills Although there is no known cure, there have been reported cases of children who recovered. Not many children with autism live independently after reaching adulthood, though some become successful An has developed, with some individuals seeking a cure and others believing autism should be accepted as a difference and not treated as a disorder. Autism is a highly variable neurodevelopmental disorder that first appears during infancy or childhood, and generally follows a steady course without remission. Overt symptoms gradually begin after the age of six months, become established by age two or three years, and tend to continue through adulthood, although often in more muted form. It is distinguished not by a single symptom, but by a characteristic triad of symptoms: impairments in social interaction; impairments in communication; and restricted interests and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis. Autism’s individual symptoms occur in the general population and appear not to associate highly, without a sharp line separating pathologically severe from common traits.
Social deficits distinguish autism and the related autism spectrum disorders (ASD; see Classification from other developmental disorders. People with autism have social impairments and often lack the intuition about others that many people take for granted. Noted autistic Temple Grandin described her inability to understand the social communication of neurotypicals, or people with normal neural development, as leaving her feeling “like an anthropologist on Mars”.
Unusual social development becomes apparent early in childhood. Autistic infants show less attention to social stimuli, smile and look at others less often, and respond less to their own name. Autistic toddlers differ more strikingly from social norms; for example, they have less eye contact and turn taking, and do not have the ability to use simple movements to express themselves, such as the deficiency to point at things. Three- to five-year-old autistic children are less likely to exhibit social understanding, approach others spontaneously, imitate and respond to emotions, communicate nonverbally, and take turns with others. However, they do form attachments to their primary caregivers. Most autistic children display moderately less attachment security than non-autistic children, although this difference disappears in children with higher mental development or less severe ASD. Older children and adults with ASD perform worse on tests of face and emotion recognition.
Children with high-functioning autism suffer from more intense and frequent loneliness compared to non-autistic peers, despite the common belief that children with autism prefer to be alone. Making and maintaining friendships often proves to be difficult for those with autism. For them, the quality of friendships, not the number of friends, predicts how lonely they feel. Functional friendships, such as those resulting in invitations to parties, may affect the quality of life more deeply.
There are many anecdotal reports, but few systematic studies, of aggression and violence in individuals with ASD. The limited data suggest that, in children with mental retardation, autism is associated with aggression, destruction of property, and tantrums. A 2007 study interviewed parents of 67 children with ASD and reported that about two-thirds of the children had periods of severe tantrums and about one-third had a history of aggression, with tantrums significantly more common than in non-autistic children with language impairments. A 2008 Swedish study found that, of individuals aged 15 or older discharged from hospital with a diagnosis of ASD, those who committed violent crimes were significantly more likely to have other psychopathological conditions such as psychosis.
About a third to a half of individuals with autism do not develop enough natural speech to meet their daily communication needs. Differences in communication may be present from the first year of life, and may include delayed onset of babbling, unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with the caregiver. In the second and third years, autistic children have less frequent and less diverse babbling, consonants, words, and word combinations; their gestures are less often integrated with words. Autistic children are less likely to make requests or share experiences, and are more likely to simply repeat others’ words (echolalia) or reverse pronouns. Joint attention seems to be necessary for functional speech, and deficits in joint attention seem to distinguish infants with ASD: for example, they may look at a pointing hand instead of the pointed-at object, and they consistently fail to point at objects in order to comment on or share an experience. Autistic children may have difficulty with imaginative play and with developing symbols into language.
In a pair of studies, high-functioning autistic children aged 8–15 performed equally well as, and adults better than, individually matched controls at basic language tasks involving vocabulary and spelling. Both autistic groups performed worse than controls at complex language tasks such as figurative language, comprehension and inference. As people are often sized up initially from their basic language skills, these studies suggest that people speaking to autistic individuals are more likely to overestimate what their audience comprehends.
Autistic individuals display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised (RBS-R)] categorizes as follows.
A young boy with autism who has arranged his toys in row
- Stereotypy is repetitive movement, such as hand flapping, head rolling, or body rocking.
- Compulsive behavior is intended and appears to follow rules, such as arranging objects in stacks or lines.
- Sameness is resistance to change; for example, insisting that the furniture not be moved or refusing to be interrupted.
- Ritualistic behavior involves an unvarying pattern of daily activities, such as an unchanging menu or a dressing ritual. This is closely associated with sameness and an independent validation has suggested combining the two factors
- Restricted behavior is limited in focus, interest, or activity, such as preoccupation with a single television program, toy, or game.
- Self-injury includes movements that injure or can injure the person, such as eye poking, skin picking, hand biting, and head banging. A 2007 study reported that self-injury at some point affected about 30% of children with ASD.
No single repetitive or self-injurious behavior seems to be specific to autism, but only autism appears to have an elevated pattern of occurrence and severity of these behaviors.
Autistic individuals may have symptoms that are independent of the diagnosis, but that can affect the individual or the family. An estimated 0.5% to 10% of individuals with ASD show unusual abilities, ranging from splinter skills such as the memorization of trivia to the extraordinarily rare talents of prodigious autistic savants. Many individuals with ASD show superior skills in perception and attention, relative to the general population. Sensory abnormalities are found in over 90% of those with autism, and are considered core features by some, although there is no good evidence that sensory symptoms differentiate autism from other developmental disorders. Differences are greater for under-responsivity (for example, walking into things) than for over-responsivity (for example, distress from loud noises) or for sensation seeking (for example, rhythmic movements). An estimated 60%–80% of autistic people have motor signs that include poor muscle tone, poor motor planning, and toe walking; deficits in motor coordination are pervasive across ASD and are greater in autism proper.
Unusual eating behavior occurs in about three-quarters of children with ASD, to the extent that it was formerly a diagnostic indicator. Selectivity is the most common problem, although eating rituals and food refusal also occur; this does not appear to result in malnutrition. Although some children with autism also have gastrointestinal (GI) symptoms, there is a lack of published rigorous data to support the theory that autistic children have more or different GI symptoms than usual; studies report conflicting results, and the relationship between GI problems and ASD is unclear.
Parents of children with ASD have higher levels of stress. Siblings of children with ASD report greater admiration of and less conflict with the affected sibling than siblings of unaffected children and were similar to siblings of children with Down syndrome in these aspects of the sibling relationship. However, they reported lower levels of closeness and intimacy than siblings of children with Down syndrome; siblings of individuals with ASD have greater risk of negative well-being and poorer sibling relationships as adults.
Autism is one of the five pervasive developmental disorders (PDD), which are characterized by widespread abnormalities of social interactions and communication, and severely restricted interests and highly repetitive behavior. These symptoms do not imply sickness, fragility, or emotional disturbance.
Of the five PDD forms, Asperger syndrome is closest to autism in signs and likely causes; Rett syndrome and childhood disintegrative disorder share several signs with autism, but may have unrelated causes; PDD not otherwise specified (PDD-NOS; also called atypical autism) is diagnosed when the criteria are not met for a more specific disorder. Unlike with autism, people with Asperger syndrome have no substantial delay in language development. The terminology of autism can be bewildering, with autism, Asperger syndrome and PDD-NOS often called the autism spectrum disorders (ASD) or sometimes the autistic disorders, whereas autism itself is often called autistic disorder, childhood autism, or infantile autism. In this article, autism refers to the classic autistic disorder; in clinical practice, though, autism, ASD, and PDD are often used interchangeably. ASD, in turn, is a subset of the broader autism phenotype, which describes individuals who may not have ASD but do have autistic-like traits, such as avoiding eye contact.
The manifestations of autism cover a wide spectrum, ranging from individuals with severe impairments—who may be silent, mentally disabled, and locked into hand flapping and rocking—to high functioning individuals who may have active but distinctly odd social approaches, narrowly focused interests, and verbose, pedantic communication Because the behavior spectrum is continuous, boundaries between diagnostic categories are necessarily somewhat arbitrary. Sometimes the syndrome is divided into low-, medium- or high-functioning autism (LFA, MFA, and HFA), based on IQ thresholds, or on how much support the individual requires in daily life; these subdivisions are not standardized and are controversial. Autism can also be divided into syndromal and non-syndromal autism; the syndromal autism is associated with severe or profound mental retardation or a congenital syndrome with physical symptoms, such as tuberous sclerosis Although individuals with Asperger syndrome tend to perform better cognitively than those with autism, the extent of the overlap between Asperger syndrome, HFA, and non-syndromal autism is unclear.
Some studies have reported diagnoses of autism in children due to a loss of language or social skills, as opposed to a failure to make progress, typically from 15 to 30 months of age. The validity of this distinction remains controversial; it is possible that regressive autism is a specific subtype, or that there is a continuum of behaviors between autism with and without regression.
Research into causes has been hampered by the inability to identify biologically meaningful subgroups within the autistic population and by the traditional boundaries between the disciplines of psychiatry, psychology, neurology and pediatrics. Newer technologies such as fMRI and diffusion tensor imaging can help identify biologically relevant phenotypes (observable traits) that can be viewed on brain scans, to help further neurogenetic studies of autism one example is lowered activity in the fusiform face area of the brain, which is associated with impaired perception of people versus objects. It has been proposed to classify autism using genetics as well as behavior.
It has long been presumed that there is a common cause at the genetic, cognitive, and neural levels for autism’s characteristic triad of symptoms. However, there is increasing suspicion that autism is instead a complex disorder whose core aspects have distinct causes that often co-occur.
Deletion (1), duplication (2) and inversion (3) are all chromosome abnormalities that have been implicated in autism.
Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether ASD is explained more by rare mutations with major effects, or by rare multigene interactions of common genetic variants. Complexity arises due to interactions among multiple genes, the environment, and epigenetic factors which do not change DNA but are heritable and influence gene expression. Studies of twins suggest that heritability is 0.7 for autism and as high as 0.9 for ASD, and siblings of those with autism are about 25 times more likely to be autistic than the general population. However, most of the mutations that increase autism risk have not been identified. Typically, autism cannot be traced to a Mendelian (single-gene) mutation or to a single chromosome abnormality, and none of the genetic syndromes associated with ASDs have been shown to selectively cause ASD. Numerous candidate genes have been located, with only small effects attributable to any particular gene. The large number of autistic individuals with unaffected family members may result from copy number variations—spontaneous deletions or duplications in genetic material during meiosis. Hence, a substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.
Several lines of evidence point to synaptic dysfunction as a cause of autism. Some rare mutations may lead to autism by disrupting some synaptic pathways, such as those involved with cell adhesion. Gene replacement studies in mice suggest that autistic symptoms are closely related to later developmental steps that depend on activity in synapses and on activity-dependent changes. All known teratogens (agents that cause birth defects) related to the risk of autism appear to act during the first eight weeks from conception, and though this does not exclude the possibility that autism can be initiated or affected later, it is strong evidence that autism arises very early in development.
Although evidence for other environmental causes is anecdotal and has not been confirmed by reliable studies, extensive searches are underway. Environmental factors that have been claimed to contribute to or exacerbate autism, or may be important in future research, include certain foods, infectious disease, heavy metals, solvents diesel exhaust, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, smoking, illicit drugs, vaccines, and prenatal stress, although no links have been found, and some have been completely disproven.
Parents may first become aware of autistic symptoms in their child around the time of a routine vaccination. This has led to unsupported theories blaming vaccine “overload”, a vaccine preservative, or the MMR vaccine for causing autism. The latter theory was supported by a litigation-funded study that has since been shown to have been “an elaborate fraud”. Although these theories lack convincing scientific evidence and are biologically implausible, parental concern about a potential vaccine link with autism has led to lower rates of childhood immunizations, outbreaks of previously controlled childhood diseases in some countries, and the preventable deaths of several children.
Autism’s symptoms result from maturation-related changes in various systems of the brain. How autism occurs is not well understood. Its mechanism can be divided into two areas: the pathophysiology of brain structures and processes associated with autism, and the neuropsychological linkages between brain structures and behaviors. The behaviors appear to have multiple pathophysiologies.
Autism affects the amygdala, cerebellum, and many other parts of the brain.
Unlike many other brain disorders, such as Parkinson’s, autism does not have a clear unifying mechanism at either the molecular, cellular, or systems level; it is not known whether autism is a few disorders caused by mutations converging on a few common molecular pathways, or is (like intellectual disability) a large set of disorders with diverse mechanisms. Autism appears to result from developmental factors that affect many or all functional brain systems, and to disturb the timing of brain development more than the final product. Neuroanatomical studies and the associations with teratogens strongly suggest that autism’s mechanism includes alteration of brain development soon after conception. This anomaly appears to start a cascade of pathological events in the brain that are significantly influenced by environmental factors. Just after birth, the brains of autistic children tend to grow faster than usual, followed by normal or relatively slower growth in childhood. It is not known whether early overgrowth occurs in all autistic children. It seems to be most prominent in brain areas underlying the development of higher cognitive specialization. Hypotheses for the cellular and molecular bases of pathological early overgrowth include the following:
- An excess of neurons that causes local overconnectivity in key brain regions.
- Disturbed neuronal migration during early gestation.
- Unbalanced excitatory–inhibitory networks.
- Abnormal formation of synapses and dendritic spines, for example, by modulation of the neurexin–neuroligin cell-adhesion system, or by poorly regulated synthesis of synaptic proteins.[ Disrupted synaptic development may also contribute to epilepsy, which may explain why the two conditions are associated.
Interactions between the immune system and the nervous system begin early during the embryonic stage of life, and successful neurodevelopment depends on a balanced immune response. Aberrant immune activity during critical periods of neurodevelopment is possibly part of the mechanism of some forms of ASD. Although some abnormalities in the immune system have been found in specific subgroups of autistic individuals, it is not known whether these abnormalities are relevant to or secondary to autism’s disease processes. As autoantibodies are found in conditions other than ASD, and are not always present in ASD, the relationship between immune disturbances and autism remains unclear and controversial.
The relationship of neurochemicals to autism is not well understood; several have been investigated, with the most evidence for the role of serotonin and of genetic differences in its transport. The role of group I metabotropic glutamate receptors (mGluR) in the pathogenesis of fragile X syndrome, the most common identified genetic cause of autism, has led to interest in the possible implications for future autism research into this pathway. Some data suggest an increase in several growth hormones; other data argue for diminished growth factors. Also, some inborn errors of metabolism are associated with autism, but probably account for less than 5% of cases.
The mirror neuron system (MNS) theory of autism hypothesizes that distortion in the development of the MNS interferes with imitation and leads to autism’s core features of social impairment and communication difficulties. The MNS operates when an animal performs an action or observes another animal perform the same action. The MNS may contribute to an individual’s understanding of other people by enabling the modeling of their behavior via embodied simulation of their actions, intentions, and emotions. Several studies have tested this hypothesis by demonstrating structural abnormalities in MNS regions of individuals with ASD, delay in the activation in the core circuit for imitation in individuals with Asperger syndrome, and a correlation between reduced MNS activity and severity of the syndrome in children with ASD. However, individuals with autism also have abnormal brain activation in many circuits outside the MNS and the MNS theory does not explain the normal performance of autistic children on imitation tasks that involve a goal or object.
Autistic individuals tend to use different areas of the brain (yellow) for a movement task compared to a control group (blue).
ASD-related patterns of low function and aberrant activation in the brain differ depending on whether the brain is doing social or nonsocial tasks In autism there is evidence for reduced functional connectivity of the default network, a large-scale brain network involved in social and emotional processing, with intact connectivity of the task-positive network, used in sustained attention and goal-directed thinking. In people with autism the two networks are not negatively correlated in time, suggesting an imbalance in toggling between the two networks, possibly reflecting a disturbance of self-referential thought. A 2008 brain-imaging study found a specific pattern of signals in the cingulate cortex which differs in individuals with ASD.
The underconnectivity theory of autism hypothesizes that autism is marked by underfunctioning high-level neural connections and synchronization, along with an excess of low-level processes. Evidence for this theory has been found in functional neuroimaging studies on autistic individuals and by a brainwave study that suggested that adults with ASD have local overconnectivity in the cortex and weak functional connections between the frontal lobe and the rest of the cortex. Other evidence suggests the underconnectivity is mainly within each hemisphere of the cortex and that autism is a disorder of the association cortex.
From studies based on event-related potentials, transient changes to the brain’s electrical activity in response to stimuli, there is considerable evidence for differences in autistic individuals with respect to attention, orientiation to auditory and visual stimuli, novelty detection, language and face processing, and information storage; several studies have found a preference for nonsocial stimuli. For example, magnetoencephalography studies have found evidence in autistic children of delayed responses in the brain’s processing of auditory signals.
In the genetic area, relations have been found between autism and schizophrenia based on duplications and deletions of chromosomes; research showed that schizophrenia and autism are significantly more common in combination with 1q21.1 deletion syndrome. Research on autism/schizophrenia relations for chromosome 15 (15q13.3), chromosome 16 (16p13.1) and chromosome 17 (17p12) are inconclusive.
Two major categories of cognitive theories have been proposed about the links between autistic brains and behavior.
The first category focuses on deficits in social cognition. The empathizing–systemizing theory postulates that autistic individuals can systemize—that is, they can develop internal rules of operation to handle events inside the brain—but are less effective at empathizing by handling events generated by other agents. An extension, the extreme male brain theory, hypothesizes that autism is an extreme case of the male brain, defined psychometrically as individuals in whom systemizing is better than empathizing; this extension is controversial, as many studies contradict the idea that baby boys and girls respond differently to people and objects.
These theories are somewhat related to the earlier theory of mind approach, which hypothesizes that autistic behavior arises from an inability to ascribe mental states to oneself and others. The theory of mind hypothesis is supported by autistic children’s atypical responses to the Sally–Anne test for reasoning about others’ motivations, and the mirror neuron system theory of autism described in Pathophysiology maps well to the hypothesis. However, most studies have found no evidence of impairment in autistic individuals’ ability to understand other people’s basic intentions or goals; instead, data suggests that impairments are found in understanding more complex social emotions or in considering others’ viewpoints.
The second category focuses on nonsocial or general processing. Executive dysfunction hypothesizes that autistic behavior results in part from deficits in working memory, planning, inhibition, and other forms of executive function. Tests of core executive processes such as eye movement tasks indicate improvement from late childhood to adolescence, but performance never reaches typical adult levels. A strength of the theory is predicting stereotyped behavior and narrow interests; two weaknesses are that executive function is hard to measure and that executive function deficits have not been found in young autistic children.
Weak central coherence theory hypothesizes that a limited ability to see the big picture underlies the central disturbance in autism. One strength of this theory is predicting special talents and peaks in performance in autistic people.A related theory—enhanced perceptual functioning—focuses more on the superiority of locally oriented and perceptual operations in autistic individuals. These theories map well from the underconnectivity theory of autism.
Neither category is satisfactory on its own; social cognition theories poorly address autism’s rigid and repetitive behaviors, while the nonsocial theories have difficulty explaining social impairment and communication difficulties. A combined theory based on multiple deficits may prove to be more useful.
About half of parents of children with ASD notice their child’s unusual behaviors by age 18 months, and about four-fifths notice by age 24 months. According to an article in the Journal of Autism and Developmental Disorders, failure to meet any of the following milestones “is an absolute indication to proceed with further evaluations. Delay in referral for such testing may delay early diagnosis and treatment and affect the long-term outcome”.
- No babbling by 12 months.
- No gesturing (pointing, waving bye-bye, etc.) by 12 months.
- No single words by 16 months.
- No two-word (spontaneous, not just echolalic) phrases by 24 months.
- Any loss of any language or social skills, at any age.
US and Japanese practice is to screen all children for ASD at 18 and 24 months, using autism-specific formal screening tests. In contrast, in the UK, children whose families or doctors recognize possible signs of autism are screened. It is not known which approach is more effective. Screening tools include the Modified Checklist for Autism in Toddlers (M-CHAT), the Early Screening of Autistic Traits Questionnaire, and the First Year Inventory; initial data on M-CHAT and its predecessor CHAT on children aged 18–30 months suggests that it is best used in a clinical setting and that it has low sensitivity (many false-negatives) but good specificity (few false-positives). It may be more accurate to precede these tests with a broadband screener that does not distinguish ASD from other developmental disorders. Screening tools designed for one culture’s norms for behaviors like eye contact may be inappropriate for a different culture. Although genetic screening for autism is generally still impractical, it can be considered in some cases, such as children with neurological symptoms and dysmorphic features.
Diagnosis is based on behavior, not cause or mechanism. Autism is defined in the DSM-IV-TR as exhibiting at least six symptoms total, including at least two symptoms of qualitative impairment in social interaction, at least one symptom of qualitative impairment in communication, and at least one symptom of restricted and repetitive behavior. Sample symptoms include lack of social or emotional reciprocity, stereotyped and repetitive use of language or idiosyncratic language, and persistent preoccupation with parts of objects. Onset must be prior to age three years, with delays or abnormal functioning in either social interaction, language as used in social communication, or symbolic or imaginative play. The disturbance must not be better accounted for by Rett syndrome or childhood disintegrative disorder. ICD-10 uses essentially the same definition.
Several diagnostic instruments are available. Two are commonly used in autism research: the Autism Diagnostic Interview-Revised (ADI-R) is a semistructured parent interview, and the Autism Diagnostic Observation Schedule (ADOS) uses observation and interaction with the child. The Childhood Autism Rating Scale (CARS) is used widely in clinical environments to assess severity of autism based on observation of children.
A pediatrician commonly performs a preliminary investigation by taking developmental history and physically examining the child. If warranted, diagnosis and evaluations are conducted with help from ASD specialists, observing and assessing cognitive, communication, family, and other factors using standardized tools, and taking into account any associated medical conditions. A pediatric neuropsychologist is often asked to assess behavior and cognitive skills, both to aid diagnosis and to help recommend educational interventions. A differential diagnosis for ASD at this stage might also consider mental retardation, hearing impairment, and a specific language impairment such as Landau–Kleffner syndrome. The presence of autism can make it harder to diagnose coexisting psychiatric disorders such as depression.
Clinical genetics evaluations are often done once ASD is diagnosed, particularly when other symptoms already suggest a genetic cause. Although genetic technology allows clinical geneticists to link an estimated 40% of cases to genetic causes, consensus guidelines in the US and UK are limited to high-resolution chromosome and fragile X testing. A genotype-first model of diagnosis has been proposed, which would routinely assess the genome’s copy number variations. As new genetic tests are developed several ethical, legal, and social issues will emerge. Commercial availability of tests may precede adequate understanding of how to use test results, given the complexity of autism’s genetics. Metabolic and neuroimaging tests are sometimes helpful, but are not routine.
ASD can sometimes be diagnosed by age 14 months, although diagnosis becomes increasingly stable over the first three years of life: for example, a one-year-old who meets diagnostic criteria for ASD is less likely than a three-year-old to continue to do so a few years later. In the UK the National Autism Plan for Children recommends at most 30 weeks from first concern to completed diagnosis and assessment, though few cases are handled that quickly in practice. A 2009 US study found the average age of formal ASD diagnosis was 5.7 years, far above recommendations, and that 27% of children remained undiagnosed at age 8 years. Although the symptoms of autism and ASD begin early in childhood, they are sometimes missed; years later, adults may seek diagnoses to help them or their friends and family understand themselves, to help their employers make adjustments, or in some locations to claim disability living allowances or other benefits.
Underdiagnosis and overdiagnosis are problems in marginal cases, and much of the recent increase in the number of reported ASD cases is likely due to changes in diagnostic practices. The increasing popularity of drug treatment options and the expansion of benefits has given providers incentives to diagnose ASD, resulting in some overdiagnosis of children with uncertain symptoms. Conversely, the cost of screening and diagnosis and the challenge of obtaining payment can inhibit or delay diagnosis. It is particularly hard to diagnose autism among the visually impaired, partly because some of its diagnostic criteria depend on vision, and partly because autistic symptoms overlap with those of common blindness syndromes or blindisms.
A three-year-old with autism points to fish in an aquarium, as part of an experiment on the effect of intensive shared-attention training on language development.
The main goals when treating children with autism are to lessen associated deficits and family distress, and to increase quality of life and functional independence. No single treatment is best and treatment is typically tailored to the child’s needs. Families and the educational system are the main resources for treatment. Studies of interventions have methodological problems that prevent definitive conclusions about efficacy. Although many psychosocial interventions have some positive evidence, suggesting that some form of treatment is preferable to no treatment, the methodological quality of systematic reviews of these studies has generally been poor, their clinical results are mostly tentative, and there is little evidence for the relative effectiveness of treatment options. Intensive, sustained special education programs and behavior therapy early in life can help children acquire self-care, social, and job skills, and often improve functioning and decrease symptom severity and maladaptive behaviors; claims that intervention by around age three years is crucial are not substantiated. Available approaches include applied behavior analysis (ABA), developmental models, structured teaching, speech and language therapy, social skills therapy, and occupational therapy.
Educational interventions can be effective to varying degrees in most children: intensive ABA treatment has demonstrated effectiveness in enhancing global functioning in preschool children and is well-established for improving intellectual performance of young children. Neuropsychological reports are often poorly communicated to educators, resulting in a gap between what a report recommends and what education is provided. It is not known whether treatment programs for children lead to significant improvements after the children grow up, and the limited research on the effectiveness of adult residential programs shows mixed results. The appropriateness of including children with varying severity of autism spectrum disorders in the general education population is a subject of current debate among educators and researchers.
Many medications are used to treat ASD symptoms that interfere with integrating a child into home or school when behavioral treatment fails. More than half of US children diagnosed with ASD are prescribed psychoactive drugs or anticonvulsants, with the most common drug classes being antidepressants, stimulants, and antipsychotics Aside from antipsychotics, there is scant reliable research about the effectiveness or safety of drug treatments for adolescents and adults with ASD. A person with ASD may respond atypically to medications, the medications can have adverse effects, and no known medication relieves autism’s core symptoms of social and communication impairments. Experiments in mice have reversed or reduced some symptoms related to autism by replacing or modulating gene function, suggesting the possibility of targeting therapies to specific rare mutations known to cause autism.
Although many alternative therapies and interventions are available, few are supported by scientific studies. Treatment approaches have little empirical support in quality-of-life contexts, and many programs focus on success measures that lack predictive validity and real-world relevance. Scientific evidence appears to matter less to service providers than program marketing, training availability, and parent requests. Some alternative treatments may place the child at risk. A 2008 study found that compared to their peers, autistic boys have significantly thinner bones if on casein-free diets; in 2005, botched chelation therapy killed a five-year-old child with autism.
Treatment is expensive; indirect costs are more so. For someone born in 2000, a US study estimated an average lifetime cost of $3.99 million (net present value in 2012 dollars, inflation-adjusted from 2003 estimate), with about 10% medical care, 30% extra education and other care, and 60% lost economic productivity. Publicly supported programs are often inadequate or inappropriate for a given child, and unreimbursed out-of-pocket medical or therapy expenses are associated with likelihood of family financial problems; one 2008 US study found a 14% average loss of annual income in families of children with ASD, and a related study found that ASD is associated with higher probability that child care problems will greatly affect parental employment. US states increasingly require private health insurance to cover autism services, shifting costs from publicly funded education programs to privately funded health insurance. After childhood, key treatment issues include residential care, job training and placement, sexuality, social skills, and estate planning.
There is no known cure. Children recover occasionally, so that they lose their diagnosis of ASD this occurs sometimes after intensive treatment and sometimes not. It is not known how often recovery happens; reported rates in unselected samples of children with ASD have ranged from 3% to 25%. Most autistic children can acquire language by age 5 or younger, though a few have developed communication skills in later years. Most children with autism lack social support, meaningful relationships, future employment opportunities or self-determination. Although core difficulties tend to persist, symptoms often become less severe with age. Few high-quality studies address long-term prognosis. Some adults show modest improvement in communication skills, but a few decline; no study has focused on autism after midlife. Acquiring language before age six, having an IQ above 50, and having a marketable skill all predict better outcomes; independent living is unlikely with severe autism. A 2004 British study of 68 adults who were diagnosed before 1980 as autistic children with IQ above 50 found that 12% achieved a high level of independence as adults, 10% had some friends and were generally in work but required some support, 19% had some independence but were generally living at home and needed considerable support and supervision in daily living, 46% needed specialist residential provision from facilities specializing in ASD with a high level of support and very limited autonomy, and 12% needed high-level hospital care. A 2005 Swedish study of 78 adults that did not exclude low IQ found worse prognosis; for example, only 4% achieved independence. A 2008 Canadian study of 48 young adults diagnosed with ASD as preschoolers found outcomes ranging through poor (46%), fair (32%), good (17%), and very good (4%); 56% of these young adults had been employed at some point during their lives, mostly in volunteer, sheltered or part-time work. Changes in diagnostic practice and increased availability of effective early intervention make it unclear whether these findings can be generalized to recently diagnosed children.
Reports of autism cases per 1,000 children grew dramatically in the US from 1996 to 2007. It is unknown how much, if any, growth came from changes in autism’s prevalence.
Most recent reviews tend to estimate a prevalence of 1–2 per 1,000 for autism and close to 6 per 1,000 for ASD, and 11 per 1,000 children in the United States for ASD as of 2008; because of inadequate data, these numbers may underestimate ASD’s true prevalence. PDD-NOS’s prevalence has been estimated at 3.7 per 1,000, Asperger syndrome at roughly 0.6 per 1,000, and childhood disintegrative disorder at 0.02 per 1,000. The number of reported cases of autism increased dramatically in the 1990s and early 2000s. This increase is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness, though unidentified environmental risk factors cannot be ruled out. The available evidence does not rule out the possibility that autism’s true prevalence has increased; a real increase would suggest directing more attention and funding toward changing environmental factors instead of continuing to focus on genetics.
Boys are at higher risk for ASD than girls. The sex ratio averages 4.3:1 and is greatly modified by cognitive impairment: it may be close to 2:1 with mental retardation and more than 5.5:1 without. Although the evidence does not implicate any single pregnancy-related risk factor as a cause of autism, the risk of autism is associated with advanced age in either parent, and with diabetes, bleeding, and use of psychiatric drugs in the mother during pregnancy. The risk is greater with older fathers than with older mothers; two potential explanations are the known increase in mutation burden in older sperm, and the hypothesis that men marry later if they carry genetic liability and show some signs of autism. Most professionals believe that race, ethnicity, and socioeconomic background do not affect the occurrence of autism.
Several other conditions are common in children with autism They include:
- Genetic disorders. About 10–15% of autism cases have an identifiable Mendelian (single-gene) condition, chromosome abnormality, or other genetic syndrome, and ASD is associated with several genetic disorders.
- Mental retardation. The fraction of autistic individuals who also meet criteria for mental retardation has been reported as anywhere from 25% to 70%, a wide variation illustrating the difficulty of assessing autistic intelligence. For ASD other than autism, the association with mental retardation is much weaker.
- Anxiety disorders are common among children with ASD; there are no firm data, but studies have reported prevalences ranging from 11% to 84%. Many anxiety disorders have symptoms that are better explained by ASD itself, or are hard to distinguish from ASD’s symptoms.
- Epilepsy, with variations in risk of epilepsy due to age, cognitive level, and type of language disorder.
- Several metabolic defects, such as phenylketonuria, are associated with autistic symptoms.
- Minor physical anomalies are significantly increased in the autistic population.
- Preempted diagnoses. Although the DSM-IV rules out concurrent diagnosis of many other conditions along with autism, the full criteria for Attention deficit hyperactivity disorder (ADHD), Tourette syndrome, and other of these conditions are often present and these comorbid diagnoses are increasingly accepted.
- Sleep problems affect about two-thirds of individuals with ASD at some point in childhood. These most commonly include symptoms of insomnia such as difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. Sleep problems are associated with difficult behaviors and family stress, and are often a focus of clinical attention over and above the primary ASD diagnosis.
Leo Kanner introduced the label early infantile autism in 1943.
A few examples of autistic symptoms and treatments were described long before autism was named. The Table Talk of Martin Luther, compiled by his notetaker, Mathesius, contains the story of a 12-year-old boy who may have been severely autistic. Luther reportedly thought the boy was a soulless mass of flesh possessed by the devil, and suggested that he be suffocated, although a later critic has cast doubt on the veracity of this report. The earliest well-documented case of autism is that of Hugh Blair of Borgue, as detailed in a 1747 court case in which his brother successfully petitioned to annul Blair’s marriage to gain Blair’s inheritance. The Wild Boy of Aveyron, a feral child caught in 1798, showed several signs of autism; the medical student Jean Itard treated him with a behavioral program designed to help him form social attachments and to induce speech via imitation.
The New Latin word autismus (English translation autism) was coined by the Swiss psychiatrist Eugen Bleuler in 1910 as he was defining symptoms of schizophrenia. He derived it from the Greek word utós (αὐτός, meaning self), and used it to mean morbid self-admiration, referring to “autistic withdrawal of the patient to his fantasies, against which any influence from outside becomes an intolerable disturbance”.
The word autism first took its modern sense in 1938 when Hans Asperger of the Vienna University Hospital adopted Bleuler’s terminology autistic psychopaths in a lecture in German about child psychology. Asperger was investigating an ASD now known as Asperger syndrome, though for various reasons it was not widely recognized as a separate diagnosis until 1981. Leo Kanner of the Johns Hopkins Hospital first used autism in its modern sense in English when he introduced the label early infantile autism in a 1943 report of 11 children with striking behavioral similarities. Almost all the characteristics described in Kanner’s first paper on the subject, notably “autistic aloneness” and “insistence on sameness”, are still regarded as typical of the autistic spectrum of disordersIt is not known whether Kanner derived the term independently of Asperger.
Kanner’s reuse of autism led to decades of confused terminology like infantile schizophrenia, and child psychiatry’s focus on maternal deprivation led to misconceptions of autism as an infant’s response to “refrigerator mothers”. Starting in the late 1960s autism was established as a separate syndrome by demonstrating that it is lifelong, distinguishing it from mental retardation and schizophrenia and from other developmental disorders, and demonstrating the benefits of involving parents in active programs of therapy. As late as the mid-1970s there was little evidence of a genetic role in autism; now it is thought to be one of the most heritable of all psychiatric conditions. Although the rise of parent organizations and the destigmatization of childhood ASD have deeply affected how we view ASD, parents continue to feel social stigma in situations where their autistic children’s behaviors are perceived negatively by others, and many primary care physicians and medical specialists still express some beliefs consistent with outdated autism research.
The Internet has helped autistic individuals bypass nonverbal cues and emotional sharing that they find so hard to deal with, and has given them a way to form online communities and work remotely. Sociological and cultural aspects of autism have developed: some in the community seek a cure, while others believe that autism is simply another way of being.