Autism and hearing loss

Discrimination in autism within different sensory modalities

Recent studies have suggested that unusual visual processing in autism might stem from enhanced visual discrimination. Although there are also many anecdotal reports of auditory and tactile processing disturbances in autism these have received comparatively little attention. It is possible that the enhanced discrimination ability in vision in autism might extend to other modalities and further that they may underlie many reports of unusual touch and audition. The present study investigated the performance of children with and without autism on auditory and tactile discrimination tasks and revealed superior auditory but comparable tactile discrimination in autism relative to controls. These results extend previous findings of perceptual discrimination in autism and may be relevant for a neuro-developmental hypothesis of the disorder.

Infection in the first 2 years of life and autism spectrum disorders

OBJECTIVE

The purpose of this work was to investigate the association between infections in the first 2 years and subsequent diagnosis of autism spectrum disorders.

METHODS

We conducted a case-control study among children born at Kaiser Permanente Northern California from 1995 to 1999. Case subjects (n = 403) were children with an autism diagnosis recorded in Kaiser Permanente databases. Control subjects (n = 2100) were randomly sampled from the remaining children without autism and frequency matched to case subjects on gender, birth year, and birth hospital. Information on infections and covariates were obtained from Kaiser Permanente and birth certificate databases.

RESULTS

Overall, infection diagnoses in the first 2 years of life were recorded slightly less often for children with autism than control children (95.0% vs 97.5%). Among specific diagnoses, upper respiratory infections were significantly less frequently diagnosed and genitourinary infections more frequently diagnosed in children with autism. In the first 30 days of life, the frequency of having an infection was slightly higher among children with autism (22.6% vs 18.7%).

CONCLUSIONS

Children with subsequent diagnoses of autism do not have more overall infections in the first 2 years of life than children without autism. Data suggest that children with autism may have modestly elevated rates of infection in the first 30 days and that, during the first 2 years, children with autism may be at higher risk for certain types of infections and lower risk for others. Additional studies that explore the associations between prenatal and early childhood infections and autism may help clarify the role of infection and the immune system in the etiology of autism spectrum disorder.

Processing of affective speech prosody is impaired in Asperger syndrome

Many people with the diagnosis of Asperger syndrome (AS) show poorly developed skills in understanding emotional messages. The present study addressed discrimination of speech prosody in children with AS at neurophysiological level. Detection of affective prosody was investigated in one-word utterances as indexed by the N1 and the mismatch negativity (MMN) of auditory event-related potentials (ERPs). Data from fourteen boys with AS were compared with those for thirteen typically developed boys. These results suggest atypical neural responses to affective prosody in children with AS and their fathers, especially over the RH, and that this impairment can already be seen at low-level information processes. Our results provide evidence for familial patterns of abnormal auditory brain reactions to prosodic features of speech.

Auditory characteristics of children with autism

OBJECTIVES

The objectives of this study were (1) to describe the auditory characteristics of children with autism relative to those of typically developing children and (2) to describe the test-retest reliability of behavioral auditory test measures with this population of children with autism.

DESIGN

Audiometric data were obtained from 22 children diagnosed with autism and 22 of their typically developing peers. The audiologic test battery consisted of behavioral measures (i.e., visual reinforcement audiometry, tangible reinforcement operant conditioning audiometry, and conditioned play audiometry) and physiological measures (auditory brain stem response audiometry, distortion product otoacoustic emissions, and acoustic reflexes).

RESULTS

Children with autism had physiologic test results equivalent to their typically developing counterparts. That is, no differences in auditory brain stem response audiometry, distortion product otoacoustic emissions, or acoustic reflex results were noted between the children with autism and typically developing children. However, behavioral measures revealed that about half of the children diagnosed with autism presented pure-tone averages outside of normal limits (i.e., >20 dB HL), although their response thresholds to speech were within normal limits. All behavioral test results were within normal limits (i.e., </=20 dB HL) for the typically developing children. In addition, test-retest variability was typically 15 dB or greater for children with autism as compared with variability of 10 dB or less for most of the typically developing children.

CONCLUSIONS

Children with autism demonstrated essentially equivalent results on a battery of physiological auditory tests as those obtained from typically developing children. However, on average, behavioral responses of children with autism were elevated and less reliable relative to those of typically developing children. Furthermore, approximately half of the children with autism demonstrated behavioral pure-tone averages outside of the normal hearing range (i.e., >20 dB HL) despite having normal to near-normal hearing sensitivity as determined by other audiometric measures.

Peripheral audition of children on the autistic spectrum

OBJECTIVE

To determine whether the peripheral audition of a group of children comprehensively diagnosed as being on the autistic spectrum was quantitatively different from that of a matched group of typically developing children.

METHODS

Thirty-seven children with autism and an equal number of control participants matched for chronological age within 6 mo were examined by means of behavioral and physiologic measures of auditory function. All participants had normal hearing (thresholds <15 dB HL; 0.25 to 8 kHz) and normal middle ear function by quantitative tympanometry. Conventional behavioral audiometry, a computer-assisted threshold assessment procedure, acoustic middle ear muscle reflex thresholds, and evoked otoacoustic emissions (both transient and distortion product) tests were administered to both groups.

RESULTS

No significant differences between children with autism and those developing typically on any behavioral or physiologic measure of peripheral auditory function were found.

CONCLUSIONS

There was no evidence of intrinsic differences in the peripheral auditory mechanism of children with autism that would account for the auditory processing disorders and sound sensitivity that are commonly reported in this population.

Response Inhibition and Immediate Arousal in Children with High-Functioning Autism

The current study compared high-functioning children with autism (HFA) and a peer control group on an immediate arousal task measuring response inhibition. In one condition go stimuli were presented whereas in another condition a tone preceded the go stimulus. The tone caused an immediate arousal effect, which resulted in a reaction time decrease and an error rate increase. It was expected that children with HFA would produce a higher error rate in comparison with normal peers, since they might be less able to suppress immediate arousal. However, the HFA group outperformed the control group, indicating neither arousal regulation deficit nor response inhibition deficit.

Sensory Experiences Questionnaire: discriminating sensory features in young children with autism, developmental delays, and typical development

BACKGROUND

This study describes a new caregiver-report assessment, the Sensory Experiences Questionnaire (SEQ), and explicates the nature of sensory patterns of hyper- and hyporesponsiveness, their prevalence, and developmental correlates in autism relative to comparison groups.

METHOD

Caregivers of 258 children in five diagnostic groups (Autism, PDD, DD/MR, Other DD, Typical) ages 5-80 months completed the SEQ.

RESULTS

The SEQ's internal consistency was alpha' = .80. Prevalence of overall sensory symptoms for the Autism group was 69%. Sensory symptoms were inversely related to mental age. The Autism group had significantly higher symptoms than either the Typical or DD groups and presented with a unique pattern of response to sensory stimuli -hyporesponsiveness in both social and nonsocial contexts. A pattern of hyperresponsiveness was similar in the Autism and DD groups, but significantly greater in both clinical groups than in the Typical group.

CONCLUSION

The SEQ was able to characterize sensory features in young children with autism, and differentiate their sensory patterns from comparison groups. These unique sensory patterns have etiological implications, as well as relevance for assessment and intervention practices.

Early medical history of children with autism spectrum disorders

Previous studies have suggested that children with autism spectrum disorders (ASD) may have different medical histories than nonspectrum children in several areas: their reactions to vaccinations, number of ear infections, chronic gastrointestinal problems, and use of antibiotics. Furthermore, some studies have found associations between regressive autism and gastrointestinal (GI) symptoms. The present study analyzes the medical records from birth to the age of 2 years of 99 children (24 typically developing; 75 with ASD, of whom 29 had parent-reported regression). Data were coded in the following areas: frequency and purpose of pediatrician visits, frequency and type of illnesses and medications, type and chronicity of GI complaints, date of vaccinations, growth data, and whether the pediatrician noted behaviors indicative of an ASD before the age of 2 years. Children with ASD were found to have significantly more ear infections than the typically developing children as well as to use significantly more antibiotics. Typically developing children had significantly more illness-related fevers. There was a nonsignificant trend toward the ASD group having more chronic gastrointestinal problems. There were no significant differences between the groups for the age of vaccination or for number of pediatrician visits. Finally, pediatricians noted symptoms of onset of possible autism, including language delay, for 44 of the 75 children with ASD and 2 of the 24 typical children. Results are discussed in terms of needs for future research.

Auditory abnormalities in autism: toward functional distinctions among findings

Recently, findings on a wide range of auditory abnormalities among individuals with autism have been reported. To date, functional distinctions among these varied findings are poorly established. Such distinctions should be of interest to clinicians and researchers alike given their potential therapeutic and experimental applications. This review suggests three general trends among these findings as a starting point for future analyses. First, studies of auditory perception of linguistic and social auditory stimuli among individuals with autism generally have found impaired perception versus normal controls. Such findings may correlate with impaired language and communication skills and social isolation observed among individuals with autism. Second, studies of auditory perception of pitch and music among individuals with autism generally have found enhanced perception versus normal controls. These findings may correlate with the restrictive and highly focused behaviors observed among individuals with autism. Third, findings on the auditory perception of non-linguistic, non-musical stimuli among autism patients resist any generalized conclusions. Ultimately, as some researchers have already suggested, the distinction between impaired global processing and enhanced local processing may prove useful in making sense of apparently discordant findings on auditory abnormalities among individuals with autism.

Aversion, awareness, and attraction: investigating claims of hyperacusis in the Williams syndrome phenotype

BACKGROUND

Williams syndrome (WS), a neurodevelopmental disorder, is characterized by pervasive cognitive deficits alongside a relative sparing of auditory perception and cognition. A frequent characteristic of the phenotype is adverse reactions to, and/or fascination with, certain sounds. Previously published reports indicate that people with WS experience hyperacusis, yet careful examination reveals that the term 'hyperacusis' has been used indiscriminately in the literature to describe quite different auditory abnormalities.

METHOD

In an effort to clarify and document the incidence of auditory abnormalities in and among people with WS we collected data from parents of people with WS (n = 118) and comparison groups of people with Down syndrome, autism, and normal controls.

RESULTS

Our findings revealed four phenomenologically separate auditory abnormalities, all of which were significantly more prevalent in WS than the three comparison groups. Among people with WS, we found relatively few reports of true hyperacusis (lowered threshold for soft sounds) or auditory fascinations/fixations, whereas 80% reported fearfulness to idiosyncratically particular sounds, and 91% reported lowered uncomfortable loudness levels, or 'odynacusis.'

CONCLUSIONS

Our results confirm anecdotal reports of an unusual auditory phenotype in WS, and provide an important foundation for understanding the nature of auditory experience and pathology in WS. We conclude by reviewing the ways in which the present findings extend and complement recent neuroanatomical and neurophysiological findings on auditory function in people with WS.

Speech and Language Development in Cognitively Delayed Children With Cochlear Implants

OBJECTIVE

The primary goals of this investigation were to examine the speech and language development of deaf children with cochlear implants and mild cognitive delay and to compare their gains with those of children with cochlear implants who do not have this additional impairment.

DESIGN

We retrospectively examined the speech and language development of 69 children with pre-lingual deafness. The experimental group consisted of 19 children with cognitive delays and no other disabilities (mean age at implantation = 38 months). The control group consisted of 50 children who did not have cognitive delays or any other identified disability. The control group was stratified by primary communication mode: half used total communication (mean age at implantation = 32 months) and the other half used oral communication (mean age at implantation = 26 months). Children were tested on a variety of standard speech and language measures and one test of auditory skill development at 6-month intervals.

RESULTS

The results from each test were collapsed from blocks of two consecutive 6-month intervals to calculate group mean scores before implantation and at 1-year intervals after implantation. The children with cognitive delays and those without such delays demonstrated significant improvement in their speech and language skills over time on every test administered. Children with cognitive delays had significantly lower scores than typically developing children on two of the three measures of receptive and expressive language and had significantly slower rates of auditory-only sentence recognition development. Finally, there were no significant group differences in auditory skill development based on parental reports or in auditory-only or multimodal word recognition.

CONCLUSIONS

The results suggest that deaf children with mild cognitive impairments benefit from cochlear implantation. Specifically, improvements are evident in their ability to perceive speech and in their reception and use of language. However, it may be reduced relative to their typically developing peers with cochlear implants, particularly in domains that require higher level skills, such as sentence recognition and receptive and expressive language. These findings suggest that children with mild cognitive deficits be considered for cochlear implantation with less trepidation than has been the case in the past. Although their speech and language gains may be tempered by their cognitive abilities, these limitations do not appear to preclude benefit from cochlear implant stimulation, as assessed by traditional measures of speech and language development.

Increased perception of loudness in autism

Clinical reports on autism describe abnormal responses to auditory stimuli such as intolerance to sounds. The present study assessed subjective perception of loudness in subjects with autism compared to healthy controls, using two psychoacoustic tests. First, the auditory dynamic range was evaluated at six different tone frequencies. Secondly, loudness growth as a function of the intensity level of a 1 kHz tone was estimated. Verbal responses from a group of 11 children and adolescents with autism were compared to responses of 11 age- and gender- matched healthy controls. Smaller auditory dynamic ranges were found in the autistic group than in the control group, as well as increased perception of loudness, indicating hyperacusis in subjects with autism.

Auditory hypersensitivity in children and teenagers with autistic spectrum disorder

OBJECTIVE

To verify if the clinical behavior of auditory hypersensitivity, reported in interviews with parents/caregivers and therapists/teachers of 46 children and teenagers suffering from autistic spectrum disorder, correspond to audiological findings.

METHOD

The clinical diagnosis for auditory hypersensitivity was investigated by means of an interview. Subsequently, a test of the acoustic stapedial reflex was conducted, and responses to intense acoustic stimulus in open field were observed.

RESULTS

Of the 46 subjects, 11 (23.9%) were clinically diagnosed as oversensitive to sound and only 2 showed discomfort when exposed to intense acoustic stimulus in open field. There was no statistically significant difference for the test of the ipsilateral acoustic stapedial reflex between the groups.

CONCLUSION

Behavioral manifestations to sounds are not associated to hypersensitivity of the auditory pathways, but instead these are associated to difficulties in the upper processing, involving systems that usually are impaired in autistic spectrum patients, such as the limbic system.

Speech-in-noise perception in high-functioning individuals with autism or Asperger's syndrome

BACKGROUND

High-functioning individuals with autism (HFA) or Asperger's syndrome (AS) commonly report difficulties understanding speech in situations where there is background speech or noise. The objective of this study was threefold: (1) to verify the validity of these reports; (2) to quantify the difficulties experienced; and (3) to propose possible mechanisms to explain the perceptual deficits described.

METHOD

Speech-in-noise perception abilities were measured using speech reception thresholds (SRTs), defined as the speech-to-noise ratio (SNR) at which approximately 50% of the speech is correctly identified. SRTs were measured for 11 individuals with HFA/AS and 9 age/IQ-matched normal-hearing control subjects, using an adaptive procedure, in a non-reverberant sound-attenuating chamber. The speech materials were standardised lists of everyday sentences spoken by a British male speaker. The background sounds were: (1) a single female talker; (2) a steady speech-shaped noise; (3) a speech-shaped noise with temporal dips; (4) a steady speech-shaped noise with regularly spaced spectral dips; and (5) a speech-shaped noise with temporal and spectral dips.

RESULTS

SRTs for the HFA/AS group were generally higher (worse) than those for the controls, across the five background sounds. A statistically significant difference in SRTs between the subject groups was found only for those background sounds that contained temporal or spectro-temporal dips. SRTs for the HFA/AS individuals were 2 to 3.5 dB higher than for the controls, equivalent to a substantial decrease in speech recognition. Expressed another way, the HFA/AS individuals required a higher SNR, whenever there were temporal dips in the background sound, to perform at the same level as the controls.

CONCLUSIONS

The results suggest that the speech-in-noise perception difficulties experienced by individuals with autism may be due, in part, to a reduced ability to integrate information from glimpses present in the temporal dips in the noise.

Otitis media with effusion

The clinical practice guideline on otitis media with effusion (OME) provides evidence-based recommendations on diagnosing and managing OME in children. This is an update of the 1994 clinical practice guideline "Otitis Media With Effusion in Young Children," which was developed by the Agency for Healthcare Policy and Research (now the Agency for Healthcare Research and Quality). In contrast to the earlier guideline, which was limited to children 1 to 3 years old with no craniofacial or neurologic abnormalities or sensory deficits, the updated guideline applies to children aged 2 months through 12 years with or without developmental disabilities or underlying conditions that predispose to OME and its sequelae. The American Academy of Pediatrics, American Academy of Family Physicians, and American Academy of Otolaryngology-Head and Neck Surgery selected a subcommittee composed of experts in the fields of primary care, otolaryngology, infectious diseases, epidemiology, hearing, speech and language, and advanced-practice nursing to revise the OME guideline. The subcommittee made a strong recommendation that clinicians use pneumatic otoscopy as the primary diagnostic method and distinguish OME from acute otitis media. The subcommittee made recommendations that clinicians should 1) document the laterality, duration of effusion, and presence and severity of associated symptoms at each assessment of the child with OME, 2) distinguish the child with OME who is at risk for speech, language, or learning problems from other children with OME and more promptly evaluate hearing, speech, language, and need for intervention in children at risk, and 3) manage the child with OME who is not at risk with watchful waiting for 3 months from the date of effusion onset (if known) or diagnosis (if onset is unknown). The subcommittee also made recommendations that 4) hearing testing be conducted when OME persists for 3 months or longer or at any time that language delay, learning problems, or a significant hearing loss is suspected in a child with OME, 5) children with persistent OME who are not at risk should be reexamined at 3- to 6-month intervals until the effusion is no longer present, significant hearing loss is identified, or structural abnormalities of the eardrum or middle ear are suspected, and 6) when a child becomes a surgical candidate (tympanostomy tube insertion is the preferred initial procedure). Adenoidectomy should not be performed unless a distinct indication exists (nasal obstruction, chronic adenoiditis); repeat surgery consists of adenoidectomy plus myringotomy with or without tube insertion. Tonsillectomy alone or myringotomy alone should not be used to treat OME. The subcommittee made negative recommendations that 1) population-based screening programs for OME not be performed in healthy, asymptomatic children, and 2) because antihistamines and decongestants are ineffective for OME, they should not be used for treatment; antimicrobials and corticosteroids do not have long-term efficacy and should not be used for routine management. The subcommittee gave as options that 1) tympanometry can be used to confirm the diagnosis of OME and 2) when children with OME are referred by the primary clinician for evaluation by an otolaryngologist, audiologist, or speech-language pathologist, the referring clinician should document the effusion duration and specific reason for referral (evaluation, surgery) and provide additional relevant information such as history of acute otitis media and developmental status of the child. The subcommittee made no recommendations for 1) complementary and alternative medicine as a treatment for OME, based on a lack of scientific evidence documenting efficacy, or 2) allergy management as a treatment for OME, based on insufficient evidence of therapeutic efficacy or a causal relationship between allergy and OME. Last, the panel compiled a list of research needs based on limitations of the evidence reviewed. The purpose of this guideline is to inform clinicians of evidence-based methods to identify, monitor, and manage OME in children aged 2 months through 12 years. The guideline may not apply to children more than 12 years old, because OME is uncommon and the natural history is likely to differ from younger children who experience rapid developmental change. The target population includes children with or without developmental disabilities or underlying conditions that predispose to OME and its sequelae. The guideline is intended for use by providers of health care to children, including primary care and specialist physicians, nurses and nurse practitioners, physician assistants, audiologists, speech-language pathologists, and child-development specialists. The guideline is applicable to any setting in which children with OME would be identified, monitored, or managed. This guideline is not intended as a sole source of guidance in evaluating children with OME. Rather, it is designed to assist primary care and other clinicians by providing an evidence-based framework for decision-making strategies. It is not intended to replace clinical judgment or establish a protocol for all children with this condition and may not provide the only appropriate approach to diagnosing and managing this problem.

Language development in autism

In this short review article, a summary of the behavioural impairments most commonly associated with the spectrum of autism-related disorders is presented, with a slightly amplified account of the defining communication impairment. The patterns of language ability and disability which typically occur in some forms of autism are then outlined, followed by a short section on possible cognitive, or psychological, explanations of these patterns. In particular, the hypothesis that defective socio-affective and socio-cognitive ('theory of mind') causes language impairments, and the hypothesis that temporal processing deficits cause these impairments, are outlined and briefly discussed. An extensive list of references is included, to support and amplify the summary data included in the review.

Learning disability

Learning disability is common, affecting 1-2.5% of the general population in the Western world, and encompasses many different conditions. It usually leads to major functional impairment and lifelong need for support and interventions, not the least important of which are medical and health-care services. Rapid progress is being made in the understanding of the cause and pathogenesis of many learning disability syndromes, and these advances are likely to improve targeted interventions in the next decade. Many countries have abolished a learning disability specialty for medical professionals, but there is a great need to revive this niche of medical knowledge. We know little about quality of life and effects on families of people with learning disability, and research is needed to address these issues.

Language and auditory processing in autism

Autism is characterized by varying degrees of disorders in language, communication and imagination. What are the prospects for making sense of this heterogeneous condition? Advances in identifying phenotypes in relation to subgroups within autism, based on disproportionate language impairment, have been recently reported by Tager-Flusberg and Joseph. The symptom severity of these subgroups requires investigation for underlying deficits, such as in auditory processing. Other recent reports support the view that a deficit in auditory processing might be a key factor in autism.

Autism and auditory brain stem responses

OBJECTIVE

To study a controversy that has been discussed for more than two decades: whether or not children with autism have abnormalities affecting the cochlear nerve or the auditory pathway in the brain stem and, if so, to describe these abnormalities.

DESIGN

A group of 153 children and adolescents with autistic disorder were included in an investigation of auditory brain stem responses (ABR). Two thirds of this group, 101 individuals (75 boys, 26 girls), had normal hearing and they were selected for an in-depth ABR study. The results from the study group were compared with those of an age-matched comparison group.

RESULTS

The III-V interpeak latency (IPL) was significantly prolonged in both boys and girls with autism, compared with the controls. The latencies of ABR waves I and V were also significantly lengthened in the study groups. The individual test results showed that more than half of this normal-hearing autistic disorder group (58%) had abnormalities of one or more of eight ABR parameters studied. The most common abnormalities were prolongation of wave V (38%), and of I-V IPL (28%). A lengthening of the I-V IPL was also recorded in 27% of 49 children who were difficult to test or who had hearing loss. Abnormal left-right differences of ABR latencies were found in 18% of autism cases with normal hearing.

CONCLUSIONS

Possible causes of the reported ABR abnormalities, observed here as well as in other studies, are discussed. Brain stem lesion, occult cochlear dysfunction, and involvement of the cochlear efferent system are probable factors that can explain the ABR findings

Low-frequency hearing assessment by middle latency responses in children with pervasive developmental disorder

OBJECTIVE

In this study, we assessed middle latency responses (MLR) in children diagnosed with pervasive developmental disorder (PDD) in order to detect low-frequency auditory thresholds.

METHODS

35 children, 25 males and 10 females, aged below 5, diagnosed with PDD were referred to rule out any possible hearing deficit. Audiologic evaluation included free-field testing, tympanometry, and both MLR and auditory brainstem responses. A control group of 15 normal children matched for sex and age were used.

RESULTS

In 9 out of 35 children (25%), low-frequency sensory hearing loss was revealed. The hearing loss was unilateral in seven children and bilateral in two, and varied from slight to severe. In four out of the nine cases (44%), parents had not suspected hearing loss, since these children always responded to sound.

CONCLUSIONS

Among children diagnosed with PDD a significant proportion (25%) was affected by low-frequency sensory hearing loss, detected by MLR. In these children, when low-frequency hearing loss was found bilateral or severe unilateral, aural rehabilitation was initiated in order to improve their responses to auditory stimuli and their impaired communication with the environment. PDD children, even if their reaction to sound is normal, must be referred to thorough audiometric evaluation while low-frequency hearing level should always be tested.

Enhanced pitch sensitivity in individuals with autism: a signal detection analysis

Past research has shown a superiority of participants with high-functioning autism over comparison groups in memorizing picture-pitch associations and in detecting pitch changes in melodies. A subset of individuals with autism, known as "musical savants," is also known to possess absolute pitch. This superiority might be due to an abnormally high sensitivity to fine-grained pitch differences in sounds. To test this hypothesis, psychoacoustic tasks were devised so as to use a signal detection methodology. Participants were all musically untrained and were divided into a group of 12 high-functioning individuals with autism and a group of 12 normally developing individuals. Their task was to judge the pitch of pure tones in a "same-different" discrimination task and in a "high-low" categorization task. In both tasks, the obtained psychometric functions revealed higher pitch sensitivity for subjects with autism, with a more pronounced advantage over control participants in the categorization task. These findings confirm that pitch processing is enhanced in "high-functioning" autism. Superior performance in pitch discrimination and categorization extends previous findings of enhanced visual performance to the auditory domain. Thus, and as predicted by the enhanced perceptual functioning model for peaks of ability in autism (Mottron & Burack, 2001), autistic individuals outperform typically developing population in a variety of low-level perceptual tasks.

Auditory brainstem response in two children with autism

Autism develops before 30 months of age. Autistic disorder is characterized by a qualitative impairment in verbal and non verbal communication, in imaginative activity, and in reciprocal social interactions. Communication in autism is so strikingly impaired that the function of the hearing system has been under study over the past 30 years, namely after the advent of physiological assessment of hearing with the auditory brainstem response (ABR). Many research studies were developed to study ABR in autism as they constitute a direct test of both hearing status and integrity of brainstem pathways, but the results obtained are contradictory. The authors present case reports of two children with autistic disorder, 2 and 4 years of age, in which the ABR findings document a prevalent Peak I in the four ears tested. This characteristic configuration in ABR has not been previously reported and future work is needed to establish the importance of this finding and its implications in the awareness of the auditory status in these children.

Sensory impairments, intellectual disability and psychiatry

The present review looks at: (1) prevalence studies of sensory impairments in people with intellectual disability (ID); (2) studies looking at psychological and psychiatric disorders in people with sensory impairments; and (3) studies that have examined the association of sensory impairments with autism. Research has indicated that sensory impairments are more common in people with ID. Psychiatric disorders are believed to be more common in children with visual impairment (VI) when associated with other handicaps. Some authors believe that hearing impairment (HI) can result in personality disorders. Studies have also shown a higher prevalence of psychiatric disorders in children with HI and a higher incidence of deaf people in psychiatric hospitals than in the general population. Psychiatric disorders in children with HI are particularly associated with low IQ and low communication ability, especially in those with multiple handicaps. There is little evidence for a higher incidence of schizophrenia in people with HI. Blind people demonstrate many autistic-like features and there has been discussion in the literature as to their cause. Deaf people also demonstrate some similar features to those in autism, but an association with autism has not been conclusively made. Deaf-blind people commonly demonstrate problem behaviour (e.g. self-injury). Usher syndrome, which is the most common cause of deaf-blindness, is associated with psychiatric disorders, particularly psychosis. The need for assessment of sensory functioning in people with ID, the difficulties inherent in this and the need for specialist services is stressed.

Autism: a novel form of mercury poisoning

Autism is a syndrome characterized by impairments in social relatedness and communication, repetitive behaviors, abnormal movements, and sensory dysfunction. Recent epidemiological studies suggest that autism may affect 1 in 150 US children. Exposure to mercury can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with autism, and the similarities extend to neuroanatomy, neurotransmitters, and biochemistry. Thimerosal, a preservative added to many vaccines, has become a major source of mercury in children who, within their first two years, may have received a quantity of mercury that exceeds safety guidelines. A review of medical literature and US government data suggests that: (i) many cases of idiopathic autism are induced by early mercury exposure from thimerosal; (ii) this type of autism represents an unrecognized mercurial syndrome; and (iii) genetic and non-genetic factors establish a predisposition whereby thimerosal's adverse effects occur only in some children.

Peripheral auditory asymmetry in infantile autism

Difficulty in filtering relevant auditory information in background noise is one of the features of autism. Auditory filtering processes can be investigated at the peripheral level as they are hypothesized to involve active cochlear mechanisms which are regulated by the efferent activity of the medial olivocochlear (MOC) system. The aim of the present work was therefore to assess these peripheral auditory processes in 22 children and adolescents with autism compared with age- and gender-matched normal controls. Active cochlear mechanisms were evaluated with transiently evoked otoacoustic emissions (TEOAEs) and MOC system efficiency was assessed via TEOAEs which are decreased when stimulating the contralateral ear with noise. The MOC system evaluation was performed on 18 of the 22 children. In both studies, results were analysed according to age (from 4 to 10 years and from 11 to 20 years). The main result concerns the asymmetry of the efferent system which differs in individuals with autism. Several neural processes might be hypothesized as involved in the results obtained as the MOC system which originates in the brainstem received regulating controls from upper brain structures including auditory cortex. Lateralization abnormalities at the auditory periphery may reflect indirectly a problem at a higher level of auditory processing. A second important result shows a decrease in TEOAE amplitude with age, in patients, that may correspond to a decrease in hearing sensitivity.