Contextual probability evaluation in autistic, receptive developmental language disorder, and control children: event-related brain potential evidence

Preliminary observations on the associations between sensory processing abnormalities and event-related potentials in adults with autism spectrum disorder

Aim

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is thought to involve a variety of neurophysiological characteristics. Event-related potentials (ERPs) reflect cognitive functions in the brain's cognitive processing. In this study, we investigated differences in P300 and N100 of ERPs between ASD and typically developing groups and focused on the relationship between the components of ERPs and measures of autistic traits and sensory processing characteristics.

Methods

ERPs were measured in 96 subjects in the ASD group and 62 subjects in the age- and sex-adjusted typically developing group. Correlations between each component and the scores of the Autism-Spectrum Quotient Japanese version (AQ-J) and the Adolescent and Adult Sensory Profile (AASP) were also evaluated.

Results

The ASD group showed a significant decrease in the amplitude of N100 at C3. Furthermore, a negative correlation was found between lower amplitude at C3 of N100 and low registered sensory scores in both groups.

Conclusion

Our findings imply that the N100 amplitude at C3 could be a potential indicator for examining the neurophysiological traits of ASD; however, these results should be interpreted with caution due to their preliminary nature. These tentative insights into sensory processing anomalies may be discernible in specific subsets of the ASD population, providing a foundation for future investigative pathways.

P300 development from infancy to adolescence

This article provides an overview of P300 research from infancy through adolescence. First, a brief historical overview is provided highlighting seminal studies that began exploration of the P300 component in developmental groups. Overall, these studies suggest that the P300 can be detected in children and appears to reflect similar cognitive processes to those in adults; however, it is significantly delayed in its latency to peak. Second, two striking findings from developmental research are the lack of a clear P300 component in infancy and differential electrophysiological responses to novel, unexpected stimuli in children, adolescents, and adults. Third, contemporary questions are described, which include P300-like components in infancy, alteration of P300 in atypically developing groups, relations between P300 and behavior, individual differences of P300, and neural substrates of P300 across development. Finally, we conclude with comments regarding the power of a developmental perspective and suggestions for important issues that should be addressed in the next 50 years of P300 research.

Electrophysiological and Behavioral Outcomes of Berard Auditory Integration Training (AIT) in Children with Autism Spectrum Disorder

Autism is a pervasive developmental disorder of childhood characterized by deficits in social interaction, language, and stereotyped behaviors along with a restricted range of interests. It is further marked by an inability to perceive and respond to social and emotional signals in a typical manner. This might due to the functional disconnectivity of networks important for specific aspects of social cognition and behavioral control resulting in deficits of sensory information integration. According to several recent theories sensory processing and integration abnormalities may play an important role in impairments of perception, cognition, and behavior in individuals with autism. Among these sensory abnormalities, auditory perception distortion may contribute to many typical symptoms of autism. The present study used Berard's technique of auditory integration training (AIT) to improve sound integration in children with autism. It also aimed to understand the abnormal neural and functional mechanisms underlying sound processing distortion in autism by incorporating behavioral, psychophysiological and neurophysiological outcomes. It was proposed that exposure to twenty 30-min AIT sessions (total 10 h of training) would result in improved behavioral evaluation scores, improve profile of cardiorespiratory activity, and positively affect both early [N1, mismatch negativity (MMN)] and late (P3) components of evoked potentials in auditory oddball task. Eighteen children with autism spectrum disorder (ASD) participated in the study. A group of 16 typically developing children served as a contrast group in the auditory oddball task. Autonomic outcomes of the study reflected a linear increase of heart rate variability measures and respiration rate. Comparison of evoked potential characteristics of children with ASD versus typically developing children revealed several group difference findings, more specifically, a delayed latency of N1 to rare and frequent stimuli, larger MMN; higher P3a to frequent stimuli, and at the same time delayed latency of P3b to rare stimuli in the autism group. Post-AIT changes in evoked potentials could be summarized as a decreased magnitude of N1 to rare stimuli, marginally lower negativity of MMN, and decrease of the P3a to frequent stimuli along with delayed latency and higher amplitude of the P3b to the rare stimuli. These evoked potential changes following completion of Berard AIT course are in a positive direction, making them less distinct from those recorded in age-matched group of typical children, thus could be considered as changes towards normalization. Parental questionnaires clearly demonstrated improvements in behavioral symptoms such as irritability, hyperactivity, repetitive behaviors and other important behavioral domains. The results of the study propose that more controlled research is necessary to document behavioral and psychophysiological changes resulting from Berard AIT and to provide explanation of the neural mechanisms of how auditory integration training may affect behavior and psychophysiological responses of children with ASD.

Meta-analysis and systematic review of the literature characterizing auditory mismatch negativity in individuals with autism

A number of past studies have used mismatch negativity (MMN) to identify auditory processing deficits in individuals with autism spectrum disorder (ASD). Our meta-analysis compared MMN responses for individuals with ASD and typically developing controls (TD). We analyzed 67 experiments across 22 publications that employed passive, auditory-based MMN paradigms with ASD and TD participants. Most studies lacked design characteristics that would lead to an accurate description of the MMN. Variability between experiments measuring MMN amplitude was smaller when limited to studies that counterbalanced stimuli. Reduced MMN amplitude was found among young children with ASD compared to controls and in experiments that used nonspeech sounds. Still, few studies included adolescents or those with below-average verbal IQ. Most studies suffered from small sample sizes, and aggregating these data did not reveal significant group differences. This analysis points to a need for research focused specifically on understudied ASD samples using carefully designed MMN experiments. Study of individual differences in MMN may provide further insights into distinct subgroups within the heterogeneous ASD population.

Atypical Processing of Novel Distracters in a Visual Oddball Task in Autism Spectrum Disorder

Several studies have shown that children with autism spectrum disorder (ASD) show abnormalities in P3b to targets in standard oddball tasks. The present study employed a three-stimulus visual oddball task with novel distracters that analyzed event-related potentials (ERP) to both target and non-target items at frontal and parietal sites. The task tested the hypothesis that children with autism are abnormally orienting attention to distracters probably due to impaired habituation to novelty. We predicted a lower selectivity in early ERPs to target, frequent non-target, and rare distracters. We also expected delayed late ERPs in autism. The study enrolled 32 ASD and 24 typically developing (TD) children. Reaction time (RT) and accuracy were analyzed as behavioral measures, while ERPs were recorded with a dense-array EEG system. Children with ASD showed higher error rate without normative post-error RT slowing and had lower error-related negativity. Parietal P1, frontal N1, as well as P3a and P3b components were higher to novels in ASD. Augmented exogenous ERPs suggest low selectivity in pre-processing of stimuli resulting in their excessive processing at later stages. The results suggest an impaired habituation to unattended stimuli that incurs a high load at the later stages of perceptual and cognitive processing and response selection when novel distracter stimuli are differentiated from targets.

P300 amplitude and latency in autism spectrum disorder: a meta-analysis

Autism spectrum disorder (ASD) is an early onset neurodevelopmental disorder. Evidence suggests that ASD patients have abnormalities in information processing. Event-related potential (ERP) technique can directly record brain neural activity in real time. P300 is a positive ERP component which can measure the neuroelectrophysiological characteristics of human beings and has the potential to discover the pathological mechanism of ASD. However, P300 studies on ASD patients are incongruent and the disparities may be caused by several factors. By searching PubMed, Embase and Cochrane Library databases, a meta-analysis of P300 component difference between ASD group and typically developed (TD) control group was conducted. Results of amplitude and latency of P3b and P3a from included studies were synthesized. Random effect model was chosen and standardized mean difference (SMD) was calculated. Subgroup analysis was used to identify the source of heterogeneity and to test the effect of different experiment factors. A total of 407 ASD patients and 457 TD controls from 32 studies were included in this analysis. Reduced amplitude of P3b was found in ASD group (SMD = -0.505, 95 % CI -0.873, -0.138) compared with TD group, but no difference of P3b latency, P3a amplitude, or P3a latency was found between groups. Subgroup analysis showed that oddball paradigm elicited attenuated P3b amplitude in Pz electrode among ASD subjects. This meta-analysis suggests ASD patients have abnormalities in P300 component, which may represent for deficits in cognition, attention orientation and working memory processing, particularly in the decision-making processing condition.

Name recognition in autism: EEG evidence of altered patterns of brain activity and connectivity

BACKGROUND

Impaired orienting to social stimuli is one of the core early symptoms of autism spectrum disorder (ASD). However, in contrast to faces, name processing has rarely been studied in individuals with ASD. Here, we investigated brain activity and functional connectivity associated with recognition of names in the high-functioning ASD group and in the control group.

METHODS

EEG was recorded in 15 young males with ASD and 15 matched one-to-one control individuals. EEG data were analyzed with the event-related potential (ERP), event-related desynchronization and event-related synchronization (ERD/S), as well as coherence and direct transfer function (DTF) methods. Four categories of names were presented visually: one's own, close-other's, famous, and unknown.

RESULTS

Differences between the ASD and control groups were found for ERP, coherence, and DTF. In individuals with ASD, P300 (a positive ERP component) to own-name and to a close-other's name were similar whereas in control participants, P300 to own-name was enhanced when compared to all other names. Analysis of coherence and DTF revealed disruption of fronto-posterior task-related connectivity in individuals with ASD within the beta range frequencies. Moreover, DTF indicated the directionality of those impaired connections-they were going from parieto-occipital to frontal regions. DTF also showed inter-group differences in short-range connectivity: weaker connections within the frontal region and stronger connections within the occipital region in the ASD group in comparison to the control group.

CONCLUSIONS

Our findings suggest a lack of the self-preference effect and impaired functioning of the attentional network during recognition of visually presented names in individuals with ASD.

Name recognition in autism: EEG evidence of altered patterns of brain activity and connectivity

Background

Impaired orienting to social stimuli is one of the core early symptoms of autism spectrum disorder (ASD). However, in contrast to faces, name processing has rarely been studied in individuals with ASD. Here, we investigated brain activity and functional connectivity associated with recognition of names in the high-functioning ASD group and in the control group.

Methods

EEG was recorded in 15 young males with ASD and 15 matched one-to-one control individuals. EEG data were analyzed with the event-related potential (ERP), event-related desynchronization and event-related synchronization (ERD/S), as well as coherence and direct transfer function (DTF) methods. Four categories of names were presented visually: one’s own, close-other’s, famous, and unknown.

Results

Differences between the ASD and control groups were found for ERP, coherence, and DTF. In individuals with ASD, P300 (a positive ERP component) to own-name and to a close-other’s name were similar whereas in control participants, P300 to own-name was enhanced when compared to all other names. Analysis of coherence and DTF revealed disruption of fronto-posterior task-related connectivity in individuals with ASD within the beta range frequencies. Moreover, DTF indicated the directionality of those impaired connections—they were going from parieto-occipital to frontal regions. DTF also showed inter-group differences in short-range connectivity: weaker connections within the frontal region and stronger connections within the occipital region in the ASD group in comparison to the control group.

Conclusions

Our findings suggest a lack of the self-preference effect and impaired functioning of the attentional network during recognition of visually presented names in individuals with ASD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13229-016-0102-z) contains supplementary material, which is available to authorized users.

Atypical sensory reactivity influences auditory attentional control in adults with autism spectrum disorders

Frequent observations of atypical sensory reactivity in people with autism spectrum disorders (ASD) suggest that the perceptual experience of those on the Spectrum is dissimilar to neurotypicals. Moreover, variable attention abilities in people with ASD, ranging from good control to periods of high distractibility, may be related to atypical sensory reactivity. This study used auditory event-related potential (ERP) measures to evaluate top-down and bottom-up attentional processes as a function of perceptual load, and examined these factors with respect to sensory reactivity. Twenty-five age and IQ-matched participants (ASD: 22.5 year, SD = 4.1 year; Controls: 22.8 year, SD = 5.1 year) completed the Adolescent/Adult Sensory Profile prior to performing a modified 3-stimulus (target, non-target, and distractor) auditory oddball target detection task EEG was recorded during task completion. ERP analysis assessed early sensory processing (P50, ∼50 ms latency; N100, ∼100 ms latency), cognitive control (N200, ∼200 ms latency), and attentional processing (P3a and P3b, ∼300 ms latency). Behavioral data demonstrates participants with ASD and neurotypical performed similarly on auditory target detection, but diverged on sensory profiles. Target ERP measures associated with top-down control (P3b latency) significantly increased under greater load in controls, but not in participants with ASD. Early ERP responses associated with bottom-up attention (P50 amplitude) were positively correlated to increased sensory sensitivity. Findings suggest specific neural mechanisms for increased perceptual capacity and enhanced bottom-up processing of sensory stimuli in people with autism. Results from participants with ASD are consistent with load theory and enhanced perceptual functioning. Autism Res 2016, 9: 1079-1092. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Tracking the sensory environment: an ERP study of probability and context updating in ASD

We recorded visual event-related brain potentials from 32 adult male participants (16 high-functioning participants diagnosed with autism spectrum disorder (ASD) and 16 control participants, ranging in age from 18 to 53 years) during a three-stimulus oddball paradigm. Target and non-target stimulus probability was varied across three probability conditions, whereas the probability of a third non-target stimulus was held constant in all conditions. P3 amplitude to target stimuli was more sensitive to probability in ASD than in typically developing participants, whereas P3 amplitude to non-target stimuli was less responsive to probability in ASD participants. This suggests that neural responses to changes in event probability are attention-dependant in high-functioning ASD. The implications of these findings for higher-level behaviors such as prediction and planning are discussed.

Attenuated auditory event-related potentials and associations with atypical sensory response patterns in children with autism

Neurobiological underpinnings of unusual sensory features in individuals with autism are unknown. Event-related potentials elicited by task-irrelevant sounds were used to elucidate neural correlates of auditory processing and associations with three common sensory response patterns (hyperresponsiveness; hyporesponsiveness; sensory seeking). Twenty-eight children with autism and 39 typically developing children (4-12 year-olds) completed an auditory oddball paradigm. Results revealed marginally attenuated P1 and N2 to standard tones and attenuated P3a to novel sounds in autism versus controls. Exploratory analyses suggested that within the autism group, attenuated N2 and P3a amplitudes were associated with greater sensory seeking behaviors for specific ranges of P1 responses. Findings suggest that attenuated early sensory as well as later attention-orienting neural responses to stimuli may underlie selective sensory features via complex mechanisms.

Atypical mismatch negativity in response to emotional voices in people with autism spectrum conditions

Autism Spectrum Conditions (ASC) are characterized by heterogeneous impairments of social reciprocity and sensory processing. Voices, similar to faces, convey socially relevant information. Whether voice processing is selectively impaired remains undetermined. This study involved recording mismatch negativity (MMN) while presenting emotionally spoken syllables dada and acoustically matched nonvocal sounds to 20 subjects with ASC and 20 healthy matched controls. The people with ASC exhibited no MMN response to emotional syllables and reduced MMN to nonvocal sounds, indicating general impairments of affective voice and acoustic discrimination. Weaker angry MMN amplitudes were associated with more autistic traits. Receiver operator characteristic analysis revealed that angry MMN amplitudes yielded a value of 0.88 (p<.001). The results suggest that people with ASC may process emotional voices in an atypical fashion already at the automatic stage. This processing abnormality can facilitate diagnosing ASC and enable social deficits in people with ASC to be predicted.

The neurology of autism: many unanswered questions

Autism is a behaviorally defined developmental disorder of the brain almost always presenting in infancy or the preschool years. Its symptoms persist life-long, although partial compensation is possible through targeted special education that addresses children's deficits in sociability, verbal and non-verbal communication, and atypical range of interests, activities, and cognitive skills. Although a majority of autistic individuals are mentally deficient, IQ is not a defining feature and verbal autistic persons of normal intelligence are increasingly being identified, referred to as Asperger syndrome. Meager neuropathologic data have disclosed subtle prenatal cellular limbic and cerebellar abnormalities. Autism is associated with a variety of defined genetic and acquired conditions, with multifactorial genetic traits, alone or interacting with environmental events, presumably responsible for most unexplained cases. Autistic regression is frequent and poorly understood and may be associated with clinical or subclinical epilepsy. Unravelling the neurobiologic basis of a disorder that may affect 1-2 in 1000 children will require a concerted multidisciplinary attack.

Atypical attentional networks and the emergence of autism

The sociocommunicative impairments that define autism spectrum disorder (ASD) are not present at birth but emerge gradually over the first two years of life. In typical development, basic attentional processes may provide a critical foundation for sociocommunicative abilities. Therefore early attentional dysfunction in ASD may result in atypical development of social communication. Prior research has demonstrated that persons with ASD exhibit early and lifelong impairments in attention. The primary aim of this paper is to provide a review of the extant research on attention in ASD using a framework of functionally independent attentional networks as conceptualized by Posner and colleagues: the alerting, orienting and executive control networks (Posner and Petersen, 1990; Petersen and Posner, 2012). The neural substrates and typical development of each attentional network are briefly discussed, a review of the ASD attention literature is presented, and a hypothesis is proposed that links aberrant attentional mechanisms, specifically impaired disengagement of attention, with the emergence of core ASD symptoms.

Auditory integration training and other sound therapies for autism spectrum disorders (ASD)

BACKGROUND

Auditory integration therapy was developed as a technique for improving abnormal sound sensitivity in individuals with behavioural disorders including autism spectrum disorders. Other sound therapies bearing similarities to auditory integration therapy include the Tomatis Method and Samonas Sound Therapy.

OBJECTIVES

To determine the effectiveness of auditory integration therapy or other methods of sound therapy in individuals with autism spectrum disorders.

SEARCH METHODS

For this update, we searched the following databases in September 2010: CENTRAL (2010, Issue 2), MEDLINE (1950 to September week 2, 2010), EMBASE (1980 to Week 38, 2010), CINAHL (1937 to current), PsycINFO (1887 to current), ERIC (1966 to current), LILACS (September 2010) and the reference lists of published papers. One new study was found for inclusion.

SELECTION CRITERIA

Randomised controlled trials involving adults or children with autism spectrum disorders. Treatment was auditory integration therapy or other sound therapies involving listening to music modified by filtering and modulation. Control groups could involve no treatment, a waiting list, usual therapy or a placebo equivalent. The outcomes were changes in core and associated features of autism spectrum disorders, auditory processing, quality of life and adverse events.

DATA COLLECTION AND ANALYSIS

Two independent review authors performed data extraction. All outcome data in the included papers were continuous. We calculated point estimates and standard errors from t-test scores and post-intervention means. Meta-analysis was inappropriate for the available data.

MAIN RESULTS

We identified six randomised comtrolled trials of auditory integration therapy and one of Tomatis therapy, involving a total of 182 individuals aged three to 39 years. Two were cross-over trials. Five trials had fewer than 20 participants. Allocation concealment was inadequate for all studies. Twenty different outcome measures were used and only two outcomes were used by three or more studies. Meta-analysis was not possible due to very high heterogeneity or the presentation of data in unusable forms. Three studies (Bettison 1996; Zollweg 1997; Mudford 2000) did not demonstrate any benefit of auditory integration therapy over control conditions. Three studies (Veale 1993; Rimland 1995; Edelson 1999) reported improvements at three months for the auditory integration therapy group based on the Aberrant Behaviour Checklist, but they used a total score rather than subgroup scores, which is of questionable validity, and Veale's results did not reach statistical significance. Rimland 1995 also reported improvements at three months in the auditory integration therapy group for the Aberrant Behaviour Checklist subgroup scores. The study addressing Tomatis therapy (Corbett 2008) described an improvement in language with no difference between treatment and control conditions and did not report on the behavioural outcomes that were used in the auditory integration therapy trials.

AUTHORS' CONCLUSIONS

There is no evidence that auditory integration therapy or other sound therapies are effective as treatments for autism spectrum disorders. As synthesis of existing data has been limited by the disparate outcome measures used between studies, there is not sufficient evidence to prove that this treatment is not effective. However, of the seven studies including 182 participants that have been reported to date, only two (with an author in common), involving a total of 35 participants, report statistically significant improvements in the auditory intergration therapy group and for only two outcome measures (Aberrant Behaviour Checklist and Fisher's Auditory Problems Checklist). As such, there is no evidence to support the use of auditory integration therapy at this time.

Auditory processing in autism spectrum disorder: a review

For individuals with autism spectrum disorder or 'ASD' the ability to accurately process and interpret auditory information is often difficult. Here we review behavioural, neurophysiological and imaging literature pertaining to this field with the aim of providing a comprehensive account of auditory processing in ASD, and thus an effective tool to aid further research. Literature was sourced from peer-reviewed journals published over the last two decades which best represent research conducted in these areas. Findings show substantial evidence for atypical processing of auditory information in ASD at behavioural and neural levels. Abnormalities are diverse, ranging from atypical perception of various low-level perceptual features (i.e. pitch, loudness) to processing of more complex auditory information such as prosody. Trends across studies suggest auditory processing impairments in ASD are most likely to present during processing of complex auditory information and are more severe for speech than for non-speech stimuli. The interpretation of these findings with respect to various cognitive accounts of ASD is discussed and suggestions offered for further research.

P300 as a measure of processing capacity in auditory and visual domains in specific language impairment

This study examined the electrophysiological correlates of auditory and visual working memory in children with Specific Language Impairments (SLI). Children with SLI and age-matched controls (11;9-14;10) completed visual and auditory working memory tasks while event-related potentials (ERPs) were recorded. In the auditory condition, children with SLI performed similarly to controls when the memory load was kept low (1-back memory load). As expected, when demands for auditory working memory were higher, children with SLI showed decreases in accuracy and attenuated P3b responses. However, children with SLI also evinced difficulties in the visual working memory tasks. In both the low (1-back) and high (2-back) memory load conditions, P3b amplitude was significantly lower for the SLI as compared to CA groups. These data suggest a domain-general working memory deficit in SLI that is manifested across auditory and visual modalities.

Low-frequency repetitive transcranial magnetic stimulation (rTMS) affects event-related potential measures of novelty processing in autism

In our previous study on individuals with autism spectrum disorder (ASD) (Sokhadze et al., Appl Psychophysiol Biofeedback 34:37-51, 2009a) we reported abnormalities in the attention-orienting frontal event-related potentials (ERP) and the sustained-attention centro-parietal ERPs in a visual oddball experiment. These results suggest that individuals with autism over-process information needed for the successful differentiation of target and novel stimuli. In the present study we examine the effects of low-frequency, repetitive Transcranial Magnetic Stimulation (rTMS) on novelty processing as well as behavior and social functioning in 13 individuals with ASD. Our hypothesis was that low-frequency rTMS application to dorsolateral prefrontal cortex (DLFPC) would result in an alteration of the cortical excitatory/inhibitory balance through the activation of inhibitory GABAergic double bouquet interneurons. We expected to find post-TMS differences in amplitude and latency of early and late ERP components. The results of our current study validate the use of low-frequency rTMS as a modulatory tool that altered the disrupted ratio of cortical excitation to inhibition in autism. After rTMS the parieto-occipital P50 amplitude decreased to novel distracters but not to targets; also the amplitude and latency to targets increased for the frontal P50 while decreasing to non-target stimuli. Low-frequency rTMS minimized early cortical responses to irrelevant stimuli and increased responses to relevant stimuli. Improved selectivity in early cortical responses lead to better stimulus differentiation at later-stage responses as was made evident by our P3b and P3a component findings. These results indicate a significant change in early, middle-latency and late ERP components at the frontal, centro-parietal, and parieto-occipital regions of interest in response to target and distracter stimuli as a result of rTMS treatment. Overall, our preliminary results show that rTMS may prove to be an important research tool or treatment modality in addressing the stimulus hypersensitivity characteristic of autism spectrum disorders.

Childhood autism and auditory system abnormalities

Hearing disorders are common among children with autism, ranging from peripheral and sensorineural hearing deficit or loss to auditory hypersensitivity with bizarre reactions to sounds. The auditory abnormalities and consequent sensory deprivation exacerbate the communication deficit of autism, and early auditory assessment holds an important place in the planning of intervention and the overall prognosis of patients. Physiologic, pathologic, imaging, and neurochemical studies have revealed an array of aberrations in the perception and processing of the audiologic stimuli, including (among others) maturational defects, atypical lateralization, and serotonin dysfunction.

Event-related potential study of novelty processing abnormalities in autism

To better understand visual processing abnormalities in autism we studied the attention orienting related frontal event potentials (ERP) and the sustained attention related centro-parietal ERPs in a three stimulus oddball experiment. The three stimulus oddball paradigm was aimed to test the hypothesis that individuals with autism abnormally orient their attention to novel distracters as compared to controls. A dense-array 128 channel EGI electroencephalographic (EEG) system was used on 11 high-functioning children and young adults with autism spectrum disorder (ASD) and 11 age-matched, typically developing control subjects. Patients with ASD showed slower reaction times but did not differ in response accuracy. At the anterior (frontal) topography the ASD group showed significantly higher amplitudes and longer latencies of early ERP components (e.g., P100, N100) to novel distracter stimuli in both hemispheres. The ASD group also showed prolonged latencies of late ERP components (e.g., P2a, N200, P3a) to novel distracter stimuli in both hemispheres. However, differences were more profound in the right hemisphere for both early and late ERP components. Our results indicate augmented and prolonged early frontal potentials and a delayed P3a component to novel stimuli, which suggest low selectivity in pre-processing and later-stage under-activation of integrative regions in the prefrontal cortices. Also, at the posterior (centro-parietal) topography the ASD group showed significantly prolonged N100 latencies and reduced amplitudes of the N2b component to target stimuli. In addition, the latency of the P3b component was prolonged to novel distracters in the ASD group. In general, the autistic group showed prolonged latencies to novel stimuli especially in the right hemisphere. These results suggest that individuals with autism over-process information needed for the successful differentiation of target and novel stimuli. We propose the potential application of ERP evaluations in a novelty task as outcome measurements in the biobehavioral treatment (e.g., EEG biofeedback, TMS) of autism.

Effects of low frequency repetitive transcranial magnetic stimulation (rTMS) on gamma frequency oscillations and event-related potentials during processing of illusory figures in autism

Previous studies by our group suggest that the neuropathology of autism is characterized by a disturbance of cortical modularity. In this model a decrease in the peripheral neuropil space of affected minicolumns provides for an inhibitory deficit and a readjustment in their signal to noise bias during information processing. In this study we proposed using low frequency transcranial magnetic stimulation (rTMS) as a way increasing the surround inhibition of minicolumns in autism. Thirteen patients (ADOS and ADI-R diagnosed) and equal number of controls participated in the study. Repetitive TMS was delivered at 0.5 Hz, 2 times per week for 3 weeks. Outcome measures based on event-related potentials (ERP), induced gamma activity, and behavioral measures showed significant post-TMS improvement. The results suggest that rTMS offers a potential therapeutic intervention for autism.

Event related potentials in the understanding of autism spectrum disorders: an analytical review

In this paper we critically review the literature on the use of event related potentials (ERPs) to elucidate the neural sources of the core deficits in autism. We review auditory and visual ERP studies, and then review the use of ERPs in the investigation of executive function. We conclude that, in autism, impairments likely exist in both low and higher level auditory and visual processing, with prominent impairments in the processing of social stimuli. We also discuss the putative neural circuitry underlying these deficits. As we look to the future, we posit that tremendous insight can be gained by applying ERPs to the definition of endophenotypes, which, in turn, can facilitate early diagnosis and the creation of informed interventions for children with autism.

Event related potentials in the understanding of autism spectrum disorders: an analytical review

In this paper we critically review the literature on the use of event related potentials (ERPs) to elucidate the neural sources of the core deficits in autism. We review auditory and visual ERP studies, and then review the use of ERPs in the investigation of executive function. We conclude that, in autism, impairments likely exist in both low and higher level auditory and visual processing, with prominent impairments in the processing of social stimuli. We also discuss the putative neural circuitry underlying these deficits. As we look to the future, we posit that tremendous insight can be gained by applying ERPs to the definition of endophenotypes, which, in turn, can facilitate early diagnosis and the creation of informed interventions for children with autism.

Brain hyper-reactivity to auditory novel targets in children with high-functioning autism

Although communication and social difficulties in autism have received a great deal of research attention, the other key diagnostic feature, extreme repetitive behaviour and unusual narrow interests, has been addressed less often. Also known as 'resistance to change' this may be related to atypical processing of infrequent, novel stimuli. This can be tested at sensory and neural levels. Our aims were to (i) examine auditory novelty detection and its neural basis in children with autism spectrum conditions (ASC) and (ii) test for brain activation patterns that correlate quantitatively with number of autistic traits as a test of the dimensional nature of ASC. The present study employed event-related fMRI during a novel auditory detection paradigm. Participants were twelve 10- to 15-year-old children with ASC and a group of 12 age-, IQ- and sex-matched typical controls. The ASC group responded faster to novel target stimuli. Group differences in brain activity mainly involved the right prefrontal-premotor and the left inferior parietal regions, which were more activated in the ASC group than in controls. In both groups, activation of prefrontal regions during target detection was positively correlated with Autism Spectrum Quotient scores measuring the number of autistic traits. These findings suggest that target detection in autism is associated not only with superior behavioural performance (shorter reaction time) but also with activation of a more widespread network of brain regions. This pattern also shows quantitative variation with number of autistic traits, in a continuum that extends to the normal population. This finding may shed light on the neurophysiological process underlying narrow interests and what clinically is called 'need for sameness'.

Electrophysiological evidence of different interpretative strategies in irony comprehension

We explore the hypothesis that induction of holistic or analytic strategies influences comprehension and processing of highly contextualized expressions of ordinary language, such as irony. Twenty undergraduate students were asked to categorize as coherent or incoherent a group of sentences. Each sentence completed a previous story, so that they could be ironical, literal or nonsensical endings. Participants were asked to evaluate whether each sentence was coherent or incoherent. Half of them were initially instructed to consider whether the sentences made sense (holistic condition); the other half were instructed to consider whether the sentences were congruent or incongruent (analytic condition). Behavioral responses and Event Related Potentials were registered during the experiment. Both behavioral and electrophysiological results allow clearly distinguishing between the holistic and the analytic strategies. The fact that the same set of stimuli elicits different ERP waveforms, depending on the strategy with which they are analyzed, suggests that different cognitive processes and different areas of the brain are operating in each case.

Mismatch negativity in children with autism and typical development

Children with autism are often characterized as having abnormalities in auditory processing. This study examined automatic and active processing of simple auditory stimuli in children using a component of event related potentials, the mismatch negativity (MMN). Amplitude of MMN in children with autism was significantly smaller than in children with typical development in unattended conditions. However, children with autism exhibited a typical amplitude MMN when attending to the stimuli. Receptive language and MMN were not related in children with autism. Findings support the idea of abnormal automatic auditory processing by children with autism. Auditory discrimination of infrequent changes in streams of sounds appears to be accomplished through a different mechanism than in typical children, specifically through the investment of attention.

Electrophysiological abnormalities of spatial attention in adults with autism during the gap overlap task

OBJECTIVE

We evaluated event-related potentials (ERPs) elicited by attentional disengagement in individuals with autism.

METHODS

Sixteen adults with autism, 17 adults with mental retardation and 14 healthy adults participated in this study. We recorded the pre-saccade positive ERPs during the gap overlap task under which a peripheral stimulus was presented subsequent to a stimulus in the central visual field. Under the overlap condition, the central stimulus remained during the presentation of the peripheral stimulus and therefore participants need to disengage their attention intentionally in order to execute the saccade to the peripheral stimulus due to the preservation of the central stimulus.

RESULTS

The autism group elicited significantly higher pre-saccadic positivity during a period of 100-70 ms prior to the saccade onset than the other groups only under the overlap condition. The higher amplitude of pre-saccadic positivity in the overlap condition was significantly correlated with more severe clinical symptoms within the autism group.

CONCLUSIONS

These results demonstrate electrophysiological abnormalities of disengagement during visuospatial attention in adults with autism which cannot be attributed to their IQs.

SIGNIFICANCE

We suggest that adults with autism have deficits in attentional disengagement and the physiological substrates underlying deficits in autism and mental retardation are different.

Adults with autism show increased sensitivity to outcomes at low error rates during decision-making

Decision-making is an important function that can be quantified using a two-choice prediction task. Individuals with Autistic Disorder (AD) often show highly restricted and repetitive behavior that may interfere with adaptive decision-making. We assessed whether AD adults showed repetitive behavior on the choice task that was unaffected by changing task demands, by examining the influence of experimenter-determined error rates on decision-making. Sixteen AD adults and 14 typically developed subjects were administered a two-choice task using three error rate conditions. Although AD subjects showed occurrences of stereotyped responding, their decision-making behavior was strongly affected by changes in task demands, especially when they experienced frequent success. Thus, behavioral paradigms that provide frequent reinforcement may be helpful in modifying decision-making abilities in AD.

Can spectro-temporal complexity explain the autistic pattern of performance on auditory tasks?

To test the hypothesis that level of neural complexity explain the relative level of performance and brain activity in autistic individuals, available behavioural, ERP and imaging findings related to the perception of increasingly complex auditory material under various processing tasks in autism were reviewed. Tasks involving simple material (pure tones) and/or low-level operations (detection, labelling, chord disembedding, detection of pitch changes) show a superior level of performance and shorter ERP latencies. In contrast, tasks involving spectrally- and temporally-dynamic material and/or complex operations (evaluation, attention) are poorly performed by autistics, or generate inferior ERP activity or brain activation. Neural complexity required to perform auditory tasks may therefore explain pattern of performance and activation of autistic individuals during auditory tasks.

Abnormal Selective Attention Normalizes P3 Amplitudes in PDD

This paper studied whether abnormal P3 amplitudes in PDD are a corollary of abnormalities in ERP components related to selective attention in visual and auditory tasks. Furthermore, this study sought to clarify possible age differences in such abnormalities. Children with PDD showed smaller P3 amplitudes than controls, but no abnormalities in selective attention. Adolescents with PDD showed abnormal selective attention, as reflected by larger auditory Processing Negativity (PN) and visual N2b, but no P3 abnormalities. Dipole localizations revealed that the locations of PN generators in subjects with PDD differed from controls. It was concluded that the abnormalities in selective attention in adolescents with PDD have a normalizing effect on P3, and possibly act as a compensatory process.

Change detection in children with autism: An auditory event-related fMRI study

Autism involves impairments in communication and social interaction, as well as high levels of repetitive, stereotypic, and ritualistic behaviours, and extreme resistance to change. This latter dimension, whilst required for a diagnosis, has received less research attention. We hypothesise that this extreme resistance to change in autism is rooted in atypical processing of unexpected stimuli. We tested this using auditory event-related fMRI to determine regional brain activity associated with passive detection of infrequently occurring frequency-deviant and complex novel sounds in a no-task condition. Participants were twelve 10- to 15-year-old children with autism and a group of 12 age- and sex-matched healthy controls. During deviance detection, significant activation common to both groups was located in the superior temporal and inferior frontal gyri. During 'novelty detection', both groups showed activity in the superior temporal gyrus, the temporo-parietal junction, the superior and inferior frontal gyri, and the cingulate gyrus. Children with autism showed reduced activation of the left anterior cingulate cortex during both deviance and novelty detection. During novelty detection, children with autism also showed reduced activation in the bilateral temporo-parietal region and in the right inferior and middle frontal areas. This study confirms previous evidence from ERP studies of atypical brain function related to automatic change detection in autism. Abnormalities involved a cortical network known to have a role in attention switching and attentional resource distribution. These results throw light on the neurophysiological processes underlying autistic 'resistance to change'.

The functional neuroanatomy of spatial attention in autism spectrum disorder

This study investigated the functional neuroanatomical correlates of spatial attention impairments in autism spectrum disorders (ASD) using an event-related functional magnetic resonance imaging (FMRI) design. Eight ASD participants and 8 normal comparison (NC) participants were tested with a task that required stimulus discrimination following a spatial cue that preceded target presentation by 100 msec (short interstimulus interval [ISI]) or 800 msec (long ISI). The ASD group showed significant behavioral spatial attention impairment in the short ISI condition. The FMRI results showed a reduction in activity within frontal, parietal, and occipital regions in ASD relative to the NC group, most notably within the inferior parietal lobule. ASD behavioral performance improved in the long ISI condition but was still impaired relative to the NC group. ASD FMRI activity in the long ISI condition suggested that the rudimentary framework of normal attention networks were engaged in ASD including bilateral activation within the frontal, parietal, and occipital lobes. Notable activation increases were observed in the superior parietal lobule and extrastriate cortex. No reliable activation was observed in the posterior cerebellar vermis in ASD participants during either long or short ISI conditions. In addition, no frontal activation during short ISI and severely reduced frontal activation during long ISI was observed in the ASD group. Taken together, these findings suggest a dysfunctional cerebello-frontal spatial attention system in ASD. The pattern of findings suggests that ASD is associated with a profound deficit in automatic spatial attention abilities and abnormal voluntary spatial attention abilities. This article also describes a method for reducing the contribution of physical eye movements to the blood-oxygenation level dependent activity in studies of ASD.

Cortical auditory evoked potentials in autism: a review

The question of etiology in autism remains elusive primarily due to the fact that autism does not result from a single dysfunction but is multi-faceted in nature. Investigations into etiology have ranged from identifying abnormalities in the genome to describing structural/functional brain abnormalities. Bearing in mind the risk of over-simplification, there is still utility in isolating a specific deficit to examine its etiologic contribution. It is known that individuals with autism have difficulty processing auditory information at the cortical level but this is not consistently seen subcortically. In recent years, cortical auditory processing has been extensively researched using event-related potentials (ERPs); however, these results in relation to autism have not been reviewed. This paper will examine this literature and discuss implications for future research.

Auditory spatial localization and attention deficits in autistic adults

The objective of this study was to compare autistic adults and matched control subjects in their ability to focus attention selectively on a sound source in a noisy environment. Event-related brain potentials (ERPs) were recorded while subjects attended to a fast paced sequence of brief noise bursts presented in free-field at a central or peripheral location. Competing sequences of noise bursts at adjacent locations were to be ignored. Both behavioral measures of target detection and auditory ERP amplitudes indicated that control subjects were able to focus their attention more sharply on the relevant sound source than autistic subjects. These findings point to a fundamental deficit in the spatial focusing of auditory attention in autism, which may be a factor that impedes social interactions and sensory-guided behavior, particularly in noisy environments.

Auditory integration training and other sound therapies for autism spectrum disorders

BACKGROUND

Autism spectrum disorders (ASD) are a heterogeneous group of disorders encompassing Autistic Disorder, Asperger's Disorder, Semantic-Pragmatic disorder and Pervasive Developmental Disorder Not Otherwise Specified. Auditory integration therapy (AIT) was developed as a technique for improving abnormal sound sensitivity in individuals with behavioural disorders including autism. Other sound therapies bearing similarities to AIT include the Tomatis Method and Samonas Sound Therapy.

OBJECTIVES

To determine the effectiveness of AIT or other methods of sound therapy in individuals with ASD.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (Cochrane Library Issue 2, 2003), MEDLINE (1966 - February 2002), EMBASE (1980 - February 2002), CINAHL (1982 - December 2001), PsycINFO (1887 - February 2002), ERIC (1965 - December 2001) and LILACS (1982 - March 2002). Reference lists of articles identified electronically were searched for further relevant publications.

SELECTION CRITERIA

Randomised controlled trials of adults or children with ASD. Treatment was auditory integration therapy (AIT) or other sound therapies involving listening to music modified by filtering and modulation. Control groups could be no treatment, waiting list, usual therapy or placebo equivalent. Outcomes sought were changes in core and associated features of ASD, auditory processing, quality of life and adverse events.

DATA COLLECTION AND ANALYSIS

All outcome data reported in included papers were continuous. Initial intention was to undertake meta-analyses using mean difference and standard deviation to take into account differences between treatment and control groups at baseline. These data were not available. Instead, point estimates and standard errors were calculated from t-test scores and post intervention means. Meta-analysis was attempted but deemed inappropriate at present.

MAIN RESULTS

No trials assessing sound therapies other than AIT were found. Six RCTs of AIT, including one cross-over trial, were identified with a total of 171 individuals aged 3-39 years. Four trials had fewer than 20 participants. Allocation concealment was inadequate for all of the studies. Seventeen different outcome measures were used. Only two outcomes were used by three or more studies: Aberrant Behaviour Checklist (ABC) (5) and Fisher's Auditory Problems Checklist (FAPC) (3). Meta-analysis was not possible due to very high heterogeneity (Aberrant Behaviour Checklist subscores), or presentation of data in unusable forms. Three studies (Bettison 1996, Zollweg 1997, Mudford 2000) did not demonstrate benefit of AIT over control conditions. The remaining trials (Veale 1993, Rimland 1995, Edelson 1999) reported improvements at 3 months for the AIT group based on improvements of total mean scores for the ABC, which is of questionable validity. Rimland 1995 also reported improvements at 3 months in the AIT group for ABC subgroup scores. No significant adverse effects of AIT were reported.

REVIEWER'S CONCLUSIONS

More research is needed to inform parents', carers' and practitioners' decision making about this therapy for individuals with autism spectrum disorders.

Auditory sensory processing in autism: a magnetoencephalographic study

BACKGROUND

Patients with autism show clinical features suggestive of abnormal processing of auditory and other sensory information. We hypothesized that low-functioning autistic subjects present abnormalities in discriminating simple auditory stimuli at sensory system preconscious stages of cortical processing.

METHODS

To verify our hypothesis, we used magnetoencephalographic measurements of mismatch field (MMF), which reflects the detection of a change in the physical characteristics of a repetitive sound. Fourteen patients (aged 8-32 years) who met DSM-IV diagnostic criteria for autistic disorder participated in an auditory oddball experiment. Ten healthy participants matched for age and gender acted as control subjects.

RESULTS

Significant differences in cerebral responses between patients and control subjects were recorded. Whereas control subjects showed a clearly identifiable MMF, with distinct generators in the M100 brain wave with regard to latency, position, and strength, no identifiable MMF was present in the autistic group.

CONCLUSIONS

Our findings suggest that low-functioning autistic subjects present a dysfunction at preconscious stages of cortical auditory discrimination, playing a role in the abnormal processing of auditory sensory afferences. The attention independence of the MMF allows for exclusion of an effect related to impaired attention or task-related responses.

The mismatch negativity and the P3a components of the auditory event-related potentials in autistic low-functioning subjects

OBJECTIVE

In order to understand better the psychophysiological basis of auditory processing abnormalities in autism, we decided to study two automatic components of the auditory event-related potentials (ERPs): the mismatch negativity (MMN)--a component of the ERP which is recorded when, during repetitive auditory stimulation, rare changes are introduced--and the novelty-related P3a which is recorded as a response to unexpected novel events occurring in a sequence of repetitive stimuli.

METHODS

Ten male subjects, mean age 12.3 years (SD 4.95), affected by autism and mental retardation were admitted to this study. All patients were also mentally retarded. Ten normal male subjects, mean age 12.2 years (SD 3.94), were used as controls. Auditory evoked potentials were recorded from 19 scalp electrodes (10-20 system), and stimuli were presented in sequences consisting of 2000 tones (70 dB, ISI=800 ms). Three types of stimuli were presented: (1) standard stimuli (1000 Hz tones, 80% of total stimuli), (2) deviant stimuli (1300 Hz tones, 10% of total stimuli), and (3) novel stimuli (complex and non-monotonal, 10% of total stimuli). To quantify the MMN, the evoked response to the standard tones was subtracted from the corresponding deviant stimulus response and its amplitude and latency at peak were measured over Fz, Cz and Pz; similarly, the P3a component of the ERP was obtained by subtracting the response to the standard tone from that to the novel stimuli and its amplitude and latency at peak were measured over Fz, Cz and Pz. Also, the amplitude and latency at peak for the N1 component of the auditory evoked potential obtained with the standard stimuli were measured over Fz, Cz and Pz. The correlation between age and MMN and P3a amplitude was also analyzed.

RESULTS

N1 showed significantly shorter latencies in the autistic groups. MMN elicited by deviant stimuli, but not that elicited by novel stimuli, was found to be significantly larger in autistic children than in normal controls. P3a showed higher amplitude in autistic subjects than in normal controls during childhood; the opposite was observed during young adulthood.

DISCUSSION

Our findings indicate that significant changes in ERPs can also be seen in non-cooperative individuals with autism and mental retardation, which might be different from the changes already reported for high-functioning autistic subjects and deserve further insight. These changes show developmental modifications that should be taken into consideration when analyzing data from autistic subjects.

Speech-sound-selective auditory impairment in children with autism: they can perceive but do not attend

In autism, severe abnormalities in social behavior coexist with aberrant attention and deficient language. In the attentional domain, attention to people and socially relevant stimuli is impaired the most. Because socially meaningful stimulus events are physically complex, a deficiency in sensory processing of complex stimuli has been suggested to contribute to aberrant attention and language in autism. This study used event-related brain potentials (ERP) to examine the sensory and early attentional processing of sounds of different complexity in high-functioning children with autism. Acoustically matched simple tones, complex tones, and vowels were presented in separate oddball sequences, in which a repetitive "standard" sound was occasionally replaced by an infrequent "deviant" sound differing from the standard in frequency (by 10%). In addition to sensory responses, deviant sounds elicited an ERP index of automatic sound-change discrimination, the mismatch negativity, and an ERP index of attentional orienting, the P3a. The sensory sound processing was intact in the high-functioning children with autism and was not affected by sound complexity or "speechness." In contrast, their involuntary orienting was affected by stimulus nature. It was normal to both simple- and complex-tone changes but was entirely abolished by vowel changes. These results demonstrate that, first, auditory orienting deficits in autism cannot be explained by sensory deficits and, second, that orienting deficit in autism might be speech-sound specific.

Event-related brain response abnormalities in autism: evidence for impaired cerebello-frontal spatial attention networks

Although under some conditions the attention-related late positive event-related potential (ERP) response (LPC) is apparently normal in autism during visual processing, the LPC elicited by visuospatial processing may be compromised. Results from this study provide evidence for abnormalities in autism in two components of the LPC generated during spatial processing. The early frontal distribution of the LPC which may reflect attention orienting was delayed or missing in autistic subjects during conditions in which attention was to peripheral visual fields. The later parietal distribution of the LPC which may be associated with context updating was smaller in amplitude in autistic subjects regardless of attention location. Both abnormalities suggest disruption of function in spatial attention networks in autism. Evidence that the cerebellar abnormalities in autism may underlie these deficits comes from: (1) similar results in ERP responses and spatial attention deficits in patients with cerebellar lesions; (2) brain-behavior correlations in normally functioning individuals associating the size of the posterior cerebellar vermis and the latency of the frontal LPC; and (3) a previously reported complementary correlation between the size of the posterior vermal lobules and spatial orienting speed. Although the scalp-recorded LPC is thought to be cortically generated, it may be modulated by subcortical neural activity. The cerebellum may serve as a modulating influence by affecting the task-related antecedent attentional process. The electrophysiological abnormalities reported here index spatial attention deficits in autism that may reflect cerebellar influence on both frontal and parietal spatial attention function.

Effects of early midline cerebellar lesion on cognitive and emotional functions in the rat

Midline lesion of the cerebellum was performed in young 10-day-old DA/HAN strained (pigmented) rats. Once adults, the lesioned animals were subjected to a series of behavioral tests and their performances were compared with those of control (nonlesioned) rats. Compared with controls, the spontaneous motor activity of the lesioned rats was higher, they showed persevering behavior and did not pay attention to environmental distractors. In anxiety and social discrimination tests, disinhibition tendencies were obvious, which suggested that the animals were less dependent on the context. These abnormalities were most likely due to early midline lesion of the cerebellum and not to a deficit in maternal care before weaning, since the dams took care of the lesioned and control pups similarly. From these results, it can be concluded that the cerebellar vermis is involved in motor control, attentional capabilities and emotional behavior. Given that the lesioned rats observed in this study presented obvious autistic-like symptoms, and since a number of autistic subjects have cerebellar deficits and, particularly, a hypoplasia of vermal lobules, our results may strengthen the idea that the cerebellar vermis is involved in autism, as already suggested in the guinea pig (Caston J, et al. Eur J Neurosci 1998;10:2677-2684).

Neural correlates of theory-of-mind reasoning: an event-related potential study

Everyday understanding of human behavior rests on having a theory of mind--the ability to relate people's actions to underlying mental states such as beliefs and desires. It has been suggested that an impaired theory of mind may lie at the heart of psychological disorders that are characterized by deficits in social understanding, such as autism. In this study, we employed the event-related potential methodology to index the activity of neural systems that are engaged during theory-of-mind reasoning in adults. Specifically, neural activity elicited by tasks that required thinking about mental as compared with nonmental representations (i.e., beliefs vs. photographs) was characterized by a focally enhanced positivity over left frontal areas, which was diminished over left parietal areas. These findings provide an important perspective on both children's theory-of-mind development and the neurobiology of disorders in which theory of mind seems to be impaired.

ERP differences among subtypes of pervasive developmental disorders

BACKGROUND

Children with multiple complex developmental disorder (MCDD) have been distinguished from autistic children on the basis of chart reviews. It was questioned whether it is possible to find other, e.g., event-related potential (ERP), evidence for this assertion.

METHODS

ERPs were measured in response to stimuli in a visual oddball task in autistic, MCDD, attention deficit disorder, dyslexic, and normal control children, to study whether ERP peaks can be used to distinguish autistic and MCDD children, and to classify the aforementioned groups.

RESULTS

It was found that the P3 at four different leads and the frontal Nc showed differences among the groups, and that the autistic and MCDD groups differed from each other as well as from the other groups. Also, it was found that, using discriminant analyses in which these parameters were included, children were classified above chance level. Especially in the MCDD group, a high percentage of correct classification was seen.

CONCLUSIONS

ERP parameters indicate that autistic and MCDD children might differ in underlying pathology and might therefore, better be regarded as two separate diagnostic entities.

An animal model of autism: behavioural studies in the GS guinea-pig

Autism is a human behavioural pathology marked by major difficulties in abnormal socialization, language comprehension and stereotypic motor patterns. These behavioural abnormalities have been associated with corticocerebral and cerebellar abnormalities in autistic patients, particularly in vermal folia VI and VII. Progress in understanding this disease has been hindered by the absence of a non-primate animal model. GS guinea-pigs are a partially inbred, non-ataxic guinea-pig strain with cerebellar and corticocerebral abnormalities similar to those reported to exist in human patients with autism. In order to determine if GS guinea-pigs represent an animal model of autism, their behaviour was compared with that of Hartley strain guinea-pigs. GS animals learned a motor task significantly more rapidly than Hartley guinea-pigs, but performed it in a more stereotypic manner and were less influenced by environmental stimuli than Hartleys. GS animals exhibited significantly less exploratory behaviour in a novel environment and were significantly less responsive to 50-95 dBA pure tones than Hartley guinea-pigs. In a social interaction assay, GS guinea-pigs interacted significantly less frequently with each other or with Hartley guinea-pigs than Hartleys did under the same conditions. GS behaviour thus exhibits autistic-like behaviour patterns: motor stereotypy, lack of exploration and response to environment and poor social interaction. Coupled with the neuropathological findings, this abnormal behaviour suggests that GS guinea-pigs could be a useful animal model of autism.

Neuropsychological and neurophysiological indices of auditory processing impairment in children with multiple complex developmental disorder

OBJECTIVE

To evaluate whether children with borderline disorder (also referred to as multiple complex developmental disorder) (BD/MCDD) and comorbid attention-deficit hyperactivity disorder (ADHD) demonstrate evidence of abnormal attention and/or auditory processing impairments as indexed by both behavioral and physiological measures.

METHOD

Three groups of children were compared in two different experiments on behavioral rating scales (Conners Parent Rating Scale and Child Behavior Checklist), behavioral accuracy to auditory and visual target detection tasks, selected neuropsychological tests, and brain physiology (event-related potentials) collected during auditory and visual target detection tasks.

RESULTS

The results demonstrate that children with BD/MCDD differ from children with ADHD in the (1) prevalence of internalizing and externalizing behaviors, (2) neuropsychological deficits related to auditory processing, and (3) event-related potential brain physiology associated with auditory cognitive target attention tasks.

CONCLUSION

Some of the pervasive pathology described in children with BD/MCDD may be due to biological vulnerabilities, particularly problems with auditory processing. Auditory processing impairments in such children deserves special attention with respect to both understanding their behavioral symptoms and developing a comprehensive treatment plan.

Quantitative EEG differences in a nonclinical sample of children with ADHD and undifferentiated ADD

OBJECTIVE

To use quantitative electroencephalographic (EEG) techniques to identify electrophysiological differences between children with distinct disorders of attention and/or hyperactivity.

METHOD

Forty children from a prescreened community sample were evaluated by means of both spectral EEG and evoked response potential (ERP) techniques. The children were 7 to 13 years of age and were selected on the basis of membership in one of the following DSM-III-R categories: attention-deficit hyperactivity disorder (ADHD) (n = 16), undifferentiated attention deficit disorder (UADD) (n = 12), or no disruptive disorder diagnosis (n = 12).

RESULTS

Spectral EEG revealed that UADD subjects had less delta band relative percent power (RPP) (p < .01), more beta band RPP (p < .01), and ERP findings of a decreased rare tone P300 amplitude (p < .02) compared with the control group. ADHD subjects had spectral EEG findings of increased beta band RPP (p < .05) and ERP findings of an increased common tone N100 latency (p < .02) and a decreased rare tone P300 amplitude (p < .02). Interhemispheric asymmetries appeared to distinguish the groups: the UADD group had spectral EEG asymmetries; the ADHD group had only ERP asymmetries; and the control group had no asymmetries.

CONCLUSION

Quantitative EEG techniques may prove useful in differentiating specific subtypes of ADHD.