Evidence for executive dysfunction in autism

Impaired task switching performance in children with dyslexia but not in children with autism

Problems with cognitive control in both autism and dyslexia have already been reported in different studies. The present study specifically examined task-switching performance in children with autism and dyslexia. For this purpose, a multiple-trial paradigm was used with cues for colour- and shape-matching tasks presented before a run of trials. The cue could imply a task switch (when the cue changed the task) or a task repetition (when the cue did not change the task). Both reaction times and error rates were measured for switching, restarting, and general task performance. Participants were children with autism (24) and with dyslexia (25) and healthy controls (27) with normal IQ and ages from 12 to 18 years. The main finding was that while similar switching performance was observed between children with autism and the healthy controls, children with dyslexia showed a significant switch-specific delay relative to both healthy controls and children with autism. Furthermore, no deficit in restarting performance was observed for any of the two patient groups. Finally, additional evidence is provided for a more general deficit in information processing in dyslexia. Our data suggest that children with autism are able to switch between tasks in a similar way as do normally developing children as long as the tasks are unambiguously specified. Furthermore, the data imply switch-specific deficits in dyslexia additionally to the deficits in general information processing already reported in the literature. The implications of our data are further discussed in relation to the interpretation of the Wisconsin Card Sorting Test.

Set-shifting in children with autism spectrum disorders: reversal shifting deficits on the Intradimensional/Extradimensional Shift Test correlate with repetitive behaviors

Research examining set-shifting has revealed significant difficulties for adults with autism spectrum disorders (ASDs). However, research with high-functioning children with ASDs has yielded mixed results. The current study tested 6- to 13-year-old high-functioning children with ASD and typically developing controls matched on age, gender, and IQ using the Intradimensional/Extradimensional (ID/ED) Shift Test from the Cambridge Neuropsychological Test Automated Battery. Children with ASDs completed as many ED shifts and reversal ED shifts as controls; however, they made significantly more errors than controls while completing the ED reversal shifts. Analyses on a subset of cases revealed a significant positive correlation between ED reversal errors and the number of repetitive behavior symptoms in the ASD group. These findings suggest that high-functioning children with ASDs require additional feedback to shift successfully. In addition, the relationship between set-shifting and non-social symptoms suggests its utility as a potentially informative intermediate phenotype in ASDs.

The relationship between theory of mind and executive function in a sample of children from mainland China

To explore the relationship between theory of mind (ToM) and executive function (EF) in a sample of individuals from mainland China, 20 children with autism spectrum disorders (ASD), 26 children with Attention Deficit Hyperactivity Disorder (ADHD), and 30 normal control subjects were compared on two batteries of ToM tasks and EF tasks. Children with ASD had a significant theory of mind impairment relative to the other controls, while non-verbal IQ removed group differences in executive function. ToM was significantly correlated with inhibitory control. Performance on inhibitory control tasks, however, did not affect performance on ToM tasks.

Corpus callosum volume and neurocognition in autism

The corpus callosum has recently been considered as an index of interhemispheric connectivity. This study applied a novel volumetric method to examine the size of the corpus callosum in 32 individuals with autism and 34 age-, gender- and IQ-matched controls and to investigate the relationship between this structure and cognitive measures linked to interhemispheric functioning. Participants with autism displayed reductions in total corpus callosum volume and in several of its subdivisions. Relationships were also observed between volumetric alterations and performance on several cognitive tests including the Tower of Hanoi test. These findings provide further evidence for anatomical alterations in the corpus callosum in autism, but warrant additional studies examining the relationship of this structure and specific measures of interhemispheric connectivity.

Examining executive functioning in children with autism spectrum disorder, attention deficit hyperactivity disorder and typical development

Executive functioning (EF) is an overarching term that refers to neuropsychological processes that enable physical, cognitive, and emotional self-control. Deficits in EF are often present in neurodevelopmental disorders, but examinations of the specificity of EF deficits and direct comparisons across disorders are rare. The current study investigated EF in 7- to 12-year-old children with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and typical development using a comprehensive battery of measures assessing EF, including response inhibition, working memory, cognitive flexibility, planning, fluency and vigilance. The ADHD group exhibited deficits in vigilance, inhibition and working memory relative to the typical group; however, they did not consistently demonstrate problems on the remaining EF measures. Children with ASD showed significant deficits in vigilance compared with the typical group, and significant differences in response inhibition, cognitive flexibility/switching, and working memory compared with both groups. These results lend support for previous findings that show children with autism demonstrate generalized and profound impairment in EF. In addition, the observed deficits in vigilance and inhibitory control suggest that a significant number of children with ASD present with cognitive profiles consistent with ADHD.

Slowed orienting of covert visual-spatial attention in autism: Specific deficits associated with cerebellar and parietal abnormality

The most commonly reported finding from structural brain studies in autism is abnormality of the cerebellum. Autopsy and magnetic resonance imaging (MR) studies from nine independent research groups have found developmental abnormality of the cerebellar vermis or hemispheres in the majority of the more than 240 subjects with autism who were studied. We reported previously that patients with autism and those with acquired damage to the cerebellum were slow to shift attention between and within sensory modalities. In this study, we found that patients with autism who come from a group with significant cerebellar abnormality were also slow to orient attention in space.

A subgroup of these patients who have additional or corollary parietal abnormality, like previously studied patients with acquired parietal damage, were also slow to detect and respond to information outside an attended location. Posner, Walker, Friedrich, and Rafal (1984) showed that patients with parietal lesions were slow to respond to contralesional information if they were attending an ipsilesional location. This study has replicated that finding in patients with autism who have developmental bilateral parietal abnormality, and found a strong correlation between the attentional deficits and the amount of neuroanatomic parietal abnormality in these patients. This is the first time in the study of autism that there is evidence for a statistically significant association of the size of a specific brain structural abnormality with a specific behavioral deficit.

These findings illustrate that in autism different patterns of underlying brain pathology may result in different patterns of functional deficits. In conjunction with previous studies of patients with acquired lesions, these data have implications for the brain bases of normal attention. The cerebellum may affect the speed with which attentional resources can be activated, while the parietal cortex affects the ability to use those resources for efficient information processing at locations outside an attended focus. Deficits in the speed and efficiency with which neural activity can be modulated to facilitate processing can clearly influence cognitive function. Such deficits may contribute to the behavioral disabilities that characterize autism.

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.

Reference production in young speakers with and without autism: effects of discourse status and processing constraints

We examine the referential choices (pronouns/zeros vs. names/descriptions) made during a narrative by high-functioning children and adolescents with autism and a well-matched typically developing control group. The process of choosing appropriate referring expressions has been proposed to depend on two areas of cognitive functioning: (a) judging the attention and knowledge of one's interlocutor, and (b) the use of memory and attention mechanisms to represent the discourse situation. We predicted possible group differences, since autism is often associated with deficits in (a) mentalizing and (b) memory and attention, as well as a more general tendency to have difficulty with the pragmatic aspects of language use. Results revealed that some of the participants with autism were significantly less likely to produce pronouns or zeros in some discourse contexts. However, the difference was only one of degree. Overall, all participants in our analysis exhibited fine-grained sensitivity to the discourse context. Furthermore, referential choices for all participants were modulated by factors related to the cognitive effort of language production.

Prenatal exposure to polychlorinated biphenyls: a neuropsychologic analysis

OBJECTIVES

A large body of literature documents the effects of prenatal exposure to polychlorinated biphenyls (PCBs) on cognitive development of children. Despite this fact, no integrative synthesis has been published yet to identify the cognitive functions that are particularly affected. Our aim is to review this literature in an attempt to identify the cognitive profile associated with prenatal PCB exposure.

DATA SOURCES

Studies were identified by searching the PubMed database for articles published before June 2008. We reviewed data from nine prospective longitudinal birth cohorts for different aspects of cognition.

DATA EXTRACTION

Associations between indicators of prenatal PCB exposure and performance on cognitive tasks reported in the selected studies are summarized and classified as general cognitive abilities, verbal or visual-spatial skills, memory, attention, and executive functions.

DATA SYNTHESIS

The most consistent effects observed across studies are impaired executive functioning related to increased prenatal PCB exposure. Negative effects on processing speed, verbal abilities, and visual recognition memory are also reported by most studies. Converging results from different cohort studies in which exposure arises from different sources make it unlikely that co-exposure with another associated contaminant is responsible for the observed effects.

CONCLUSION

Prenatal PCB exposure appears to be related to a relatively specific cognitive profile of impairments. Failure to assess functions that are specifically impaired may explain the absence of effects found in some studies. Our findings have implications in the selection of cognitive assessment methods in future studies.

Atypical modulation of cognitive control by arousal in autism

We examined the effects of viewing high-arousal pictures on regional brain activations elicited by a cognitive control task in participants with high-functioning autism and neurotypical controls. Specifically, using event-related functional magnetic resonance imaging, we assessed the effects of brief presentations of highly arousing pictures (i.e., both very pleasant and very unpleasant) on the processing of stimuli requiring cognitive control. Similar to previous findings, when stimuli with high cognitive control demands were preceded by low-arousal pictures, individuals with autism demonstrated regional brain activations that were comparable to neurotypical control individuals. When the presentation of the cognitive control stimuli was preceded by high-arousal pictures, however, the control group was characterized by relatively greater activation in the right lateral midfrontal cortex in response to cognitive control stimuli. In contrast, preceding high-arousal stimuli did not modulate activity elicited in this region by cognitive control stimuli in the autism group. Differential modulation of right lateral midfrontal activation by high-arousal stimuli in autism is consistent with the "inefficiency model" of brain functioning in autism spectrum disorders, and contributes to a growing body of evidence that autism may be characterized by anomalous sensitivity of cognitive control brain regions to social-emotional context.

Size sequencing as a window on executive control in children with autism and Asperger's syndrome

A study is reported in which size sequencing on a touch screen is used as a measure of executive control in 20 high-functioning children with Autistic Spectrum Disorders (ASD). The data show a significant and age-independent effect of the length of sequence that can be executed without errors by these children, in comparison with a chronologically age-matched group of children with normal development. Error data and reaction times are analysed and are interpreted as revealing a constraint on the prospective component of working memory in children on the autistic spectrum even when there is no change in goal or perceptual set. It is concluded that the size sequencing paradigm is an effective measure of executive difficulties associated with autism.

Evidence for impairments in using static line drawings of eye gaze cues to orient visual-spatial attention in children with high functioning autism

We examined the ability to use static line drawings of eye gaze cues to orient visual-spatial attention in children with high functioning autism (HFA) compared to typically developing children (TD). The task was organized such that on valid trials, gaze cues were directed toward the same spatial location as the appearance of an upcoming target, while on invalid trials gaze cues were directed to an opposite location. Unlike TD children, children with HFA showed no advantage in reaction time (RT) on valid trials compared to invalid trials (i.e., no significant validity effect). The two stimulus onset asynchronies (200 ms, 700 ms) did not differentially affect these findings. The results suggest that children with HFA show impairments in utilizing static line drawings of gaze cues to orient visual-spatial attention.

Profiling executive dysfunction in adults with autism and comorbid learning disability

Executive dysfunction is thought to be primary to autism. We examined differences in executive function between 20 adults with autism and learning disability and 23 individuals with learning disabilities outside the autistic spectrum. All participants were matched for chronological age and full-scale IQ, and were given a battery of tasks assessing fluency, planning, set-shifting, inhibition and working memory. Analyses of the individual tasks revealed very few significant differences between the two groups. However, analyses of composite scores derived for each executive domain revealed that the group with autism showed impaired performance on the working memory and planning tests. Together, these two measures were sufficient to classify participants into their diagnostic groups significantly better than would be expected by chance (75% of the autism group; 65% of the control group). Executive impairments were neither universal nor exclusive to the autism group, and we suggest that an alternative cognitive theory may better explain the cognitive profile we found.

Autistic traits and cognitive performance in young people with mild intellectual impairment

Cognitive performance and the relationship between theory of mind (TOM), weak central coherence and executive function were investigated in a cohort of young people with additional learning needs. Participants were categorized by social communication questionnaire score into groups of 10 individuals within the autistic spectrum disorder (ASD) range, 14 within the pervasive developmental disorder range and 18 with few autistic traits. The ASD group were significantly poorer than the other groups on a test of cognitive flexibility. In the ASD group only, there was a strong relationship between executive performance and TOM which remained after controlling for IQ. Our findings suggest that the relationship between cognitive traits may more reliably distinguish autism than the presence of individual deficits alone.

A DRD1 haplotype is associated with risk for autism spectrum disorders in male-only affected sib-pair families

Individuals with autism spectrum disorders (ASDs) have impairments in executive function and social cognition, with males generally being more severely affected in these areas than females. Because the dopamine D1 receptor (encoded by DRD1) is integral to the neural circuitry mediating these processes, we examined the DRD1 gene for its role in susceptibility to ASDs by performing single marker and haplotype case-control comparisons, family-based association tests, and genotype-phenotype assessments (quantitative transmission disequilibrium tests: QTDT) using three DRD1 polymorphisms, rs265981C/T, rs4532A/G, and rs686T/C. Our previous findings suggested that the dopaminergic system may be more integrally involved in families with affected males only than in other families. We therefore restricted our study to families with two or more affected males (N = 112). There was over-transmission of rs265981-C and rs4532-A in these families (P = 0.040, P = 0.038), with haplotype TDT analysis showing over-transmission of the C-A-T haplotype (P = 0.022) from mothers to affected sons (P = 0.013). In addition, haplotype case-control comparisons revealed an increase of this putative risk haplotype in affected individuals relative to a comparison group (P = 0.004). QTDT analyses showed associations of the rs265981-C, rs4532-A, rs686-T alleles, and the C-A-T haplotype with more severe problems in social interaction, greater difficulties with nonverbal communication and increased stereotypies compared to individuals with other haplotypes. Preferential haplotype transmission of markers at the DRD1 locus and an increased frequency of a specific haplotype support the DRD1 gene as a risk gene for core symptoms of ASD in families having only affected males.

The neural circuitry mediating shifts in behavioral response and cognitive set in autism

BACKGROUND

Recent studies have suggested that the social and cognitive impairments in autism are associated with neural processing deficits in specific brain regions. However, these studies have primarily focused on neural systems responsible for face processing and social behaviors. Although repetitive, stereotyped behaviors are a hallmark of autism, little is known about the neural mechanisms underlying these behaviors in the disorder.

METHODS

We used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of shifts in behavioral response and cognitive set in 18 individuals with high-functioning autism and 15 neurotypical control participants. Participants performed a target detection task specifically designed to distinguish shifts in response from shifts in cognitive set.

RESULTS

Individuals with autism showed lower accuracy on response shifting trials, independent of whether those trials also required a shift in cognitive set. Compared with control subjects, participants with autism showed reduced activation in frontal, striatal, and parietal regions during these trials. In addition, within the autism group, the severity of restricted, repetitive behaviors was negatively correlated with activation in anterior cingulate and posterior parietal regions.

CONCLUSIONS

These results suggest that executive deficits and, by extension, repetitive behaviors associated with autism might reflect a core dysfunction within the brain's executive circuitry.

The role of control functions in mentalizing: Dual-task studies of Theory of Mind and executive function

Conflicting evidence has arisen from correlational studies regarding the role of executive control functions in Theory of Mind. The current study used dual-task manipulations of executive functions (inhibition, updating and switching) to investigate the role of these control functions in mental state and non-mental state tasks. The 'Eyes' pictorial test of Theory of Mind showed specific dual-task costs when concurrently performed with an inhibitory secondary task. In contrast, interference effects on a verbal 'Stories' task were general, occurring on both mental state and non-mental state tasks, and across all types of executive function. These findings from healthy functioning adults should help to guide decisions about appropriate methods of assessing ToM in clinical populations, and interpreting deficits in performance in such tasks in the context of more general cognitive dysfunction.

Do theory of mind and executive function deficits underlie the adverse outcomes associated with profound early deprivation?: findings from the English and Romanian adoptees study

Theory of Mind (ToM) and Executive Function (EF) have been associated with autism and with attention-deficit hyperactivity disorder (ADHD), and hence might play a role in similar syndromes found following profound early institutional deprivation. In order to examine this possibility the current study included a group of 165 Romanian adoptees, of whom 144 were adopted into the UK from deprived institutional settings before 43months of age, and a group of 52 within-UK adoptees, all adopted before 6months of age. Both groups were assessed at 6 and 11years. The Strange Stories task was used to assess ToM and the Stroop task was used to assess EF, both at age 11. The Romanian adoptees displayed deficits in both ToM and EF compared with the within-UK adoptee group. The degree of deficit was greater for children who had experienced more than 6months of institutional deprivation. Deficits in both domains (ToM and EF) were associated with each of the three apparently deprivation-specific problems, namely quasi-autism, disinhibited attachment and inattention/overactivity. Statistical analyses indicated a mediating role for both ToM and EF with respect to quasi-autism; possibly a partial mediating role for EF with respect to inattention/overactivity; and probably no mediating role for either ToM or EF in the case of disinhibited attachment. In conclusion, there is evidence for a possible mediating role for ToM and EF in the development of some apparently deprivation-specific difficulties in institution-reared Romanian adoptees, but neither accounts for the overall pattern of deprivation-related difficulties.

fMRI investigation of working memory for faces in autism: visual coding and underconnectivity with frontal areas

Brain activation and functional connectivity were investigated in high functioning autism using functional magnetic resonance imaging in an n-back working memory task involving photographic face stimuli. The autism group showed reliably lower activation compared with controls in the inferior left prefrontal area (involved in verbal processing and working memory maintenance) and the right posterior temporal area (associated with theory of mind processing). The participants with autism also showed activation in a somewhat different location in the fusiform area than the control participants. These results suggest that the neural circuitry of the brain for face processing in autism may be analyzing the features of the face more as objects and less in terms of their human significance. The functional connectivity results revealed that the abnormal fusiform activation was embedded in a larger context of smaller and less synchronized networks, particularly indicating lower functional connectivity with frontal areas. In contrast to the underconnectivity with frontal areas, the autism group showed no underconnectivity among posterior cortical regions. These results extend previous findings of abnormal face perception in autism by demonstrating that the abnormalities are embedded in an abnormal cortical network that manages to perform the working memory task proficiently, using a visually oriented, asocial processing style that minimizes reliance on prefrontal areas.

Learning, attention, writing, and processing speed in typical children and children with ADHD, autism, anxiety, depression, and oppositional-defiant disorder

Learning, attention, graphomotor, and processing speed scores were analyzed in 149 typical control children and 886 clinical children with normal intelligence. Nonsignificant differences were found between control children and children with anxiety, depression, and oppositional-defiant disorder. Control children performed better than children with ADHD and autism in all areas. Children with ADHD and autism did not differ, except that children with ADHD had greater learning problems. Attention, graphomotor, and speed weaknesses were likely to coexist, the majority of children with autism and ADHD had weaknesses in all three areas, and these scores contributed significantly to the prediction of academic achievement.

Endophenotypes in eating disorders: moving toward etiologically based diagnosis and treatment focused on pathophysiology

It is hoped that the greater understanding neuroscience will bring to the field of psychiatry will lead to a more biologically based system of classification and diagnosis for psychiatric disorders. The clarification of endophenotypes might produce the ‘macros’ from which such a system could be constructed. The aim of this paper is to discuss the evidence for continuities between eating disorders and developmental disorders of childhood (autistic spectrum disorders and attention-deficit hyperactivity disorder) and possible shared endophenotypes. We review the evidence for obsessive–compulsive traits and disinhibition as intermediate phenotypes, and for information-processing styles such as weak set shifting, central coherence, disinhibition and reward sensitivity as possible endophenotypes. Finally we discuss the implications that this has for treatment.

Social and behavioral problems of children with agenesis of the corpus callosum

Archival data from a survey of parent observations was used to determine the prevalence of social and behavioral problems in children with agenesis of the corpus callosum (ACC). Parent observations were surveyed using the Child Behavior Checklist (CBCL) for 61 children with ACC who were selected from the archive based on criteria of motor development suggesting a relatively high general level of functioning. Younger children with ACC (ages 2-5) were rated as primarily having problems with sleep. Older children with ACC (ages 6-11) manifested problems in attention, social function, thought, and somatic complaints. The older children with ACC were also compared to CBCL data from 52 children with autism who were selected from a previous study. Children with ACC were generally less impaired than children with autism on nearly all scales, with significantly less severe problems in the areas of attention, anxiety/depression, social function, and unusual thoughts. A further questionnaire related to diagnostic criteria for autism indicated that some children with ACC had traits that are among those that contribute to the diagnosis of autism within the domains of social interaction and social communication, but fewer who manifest repetitive and restricted behaviors.

A longitudinal study of pretend play in autism

This study describes a longitudinal design (following subjects described in Rutherford & Rogers [2003, Journal of Autism and Developmental Disorder, 33, 289-302]) to test for predictors of pretend play competence in a group of children with autism. We tested the hypothesis that developmental change in pretend play performance can be predicted by earlier measures of either executive function, intersubjectivity, imitation, or general development. Participants at the time of follow-up testing were 28 children with autistic disorder (mean chronological age (CA) 57.6 months), 18 children with other developmental disorders (mean CA 59.0 months), and 27 typically developing children (mean CA 30.1 months). Children with autism were profoundly delayed given both competence (prompted) measures as well as performance (spontaneous) measures. Joint attention at time 1 strongly and uniquely predicted pretend play development.

Executive function in preschoolers with autism: evidence consistent with a secondary deficit

Recent research on executive function (EF) deficits in autism has led investigators to conclude that EF deficits are secondary to the disorder. The current study has two major goals: (1) Examine whether specific EF deficits are present in the youngest autism group to date (mean=2.9 years), and (2) examine whether such deficits are secondary to autism, or act as an early non-specific cognitive risk factor for autism by comparing EF abilities of this autism group to a CA-matched typically developing group. Results from Experiment 1 suggest no specific EF deficits in autism relative to MA-matched controls, while results from Experiment 2 are consistent with the hypothesis that EF deficits may emerge as a secondary deficit in autism. Alternative hypotheses are also considered.

Tactile sensitivity of normal and autistic children

Many children with autistic spectrum disorders have unusual reactions to certain sensory stimuli. These reactions vary along a hyper- to hypo-responsivity continuum. For example, some children overreact to weak sensory input, but others do not respond negatively to even strong stimuli. It is typically assumed that this deviant responsivity is linked to sensitivity, although the particular stage of sensory processing affected is not known. Psychophysical vibrotactile thresholds of six male children (age: 8-12) who were diagnosed to have autistic spectrum disorders and six normal male children (age: 7-11) were measured by using a two-alternative forced-choice task. The tactile stimuli were sinusoidal displacements and they were applied on the terminal phalanx of the left middle finger of each subject. By using a forward-masking paradigm, 40- and 250-Hz thresholds of the Pacinian tactile channel and 40-Hz threshold of the Non-Pacinian I tactile channel were determined. There was no significant difference between the thresholds of autistic and normal children, and the autistic children had the same detection and masking mechanisms as the normal children. The sensory responsivity of each subject was tested by clinical questionnaires, which showed again no difference between the two subject groups. Furthermore, no significant correlations could be found between the questionnaire data and the psychophysical thresholds. However, there was a high correlation between the data from the tactile and emotional subsets of the questionnaires. These results support the hypothesis that the hyper- and hypo-responsivity to touch, which is sometimes observed in autistic spectrum disorders, is not a perceptual sensory problem, but may probably be emotional in origin.

A neurobehavioral examination of individuals with high-functioning autism and Asperger's disorder using a fronto-striatal model of dysfunction

The repetitive, stereotyped, and obsessive behaviors that characterize autism may in part be attributable to disruption of the region of the fronto-striatal system, which mediates executive abilities. Neuropsychological testing has shown that children with autism exhibit set-shifting deficiencies on tests such as the Wisconsin Card Sorting task but show normal inhibitory ability on variants of the Stroop color-word test. According to Minshew and Goldstein's multiple primary deficit theory, the complexity of the executive functioning task is important in determining the performance of individuals with autism. This study employed a visual-spatial task (with a Stroop-type component) to examine the integrity of executive functioning, in particular inhibition, in autism (n = 12) and Asperger's disorder (n = 12) under increasing levels of cognitive complexity. Whereas the Asperger's disorder group performed similarly to age- and IQ-matched control participants, even at the higher levels of cognitive complexity, the high-functioning autism group displayed inhibitory deficits specifically associated with increasing cognitive load.

The elusive nature of executive functions: a review of our current understanding

Executive functions include abilities of goal formation, planning, carrying out goal-directed plans, and effective performance. This article aims at reviewing some of the current knowledge surrounding executive functioning and presenting the contrasting views regarding this concept. The neural substrates of the executive system are examined as well as the evolution of executive functioning, from development to decline. There is clear evidence of the vulnerability of executive functions to the effects of age over lifespan. The first executive function to emerge in children is the ability to inhibit overlearned behavior and the last to appear is verbal fluency. Inhibition of irrelevant information seems to decline earlier than set shifting and verbal fluency during senescence. The sequential progression and decline of these functions has been paralleled with the anatomical changes of the frontal lobe and its connections with other brain areas. Generalization of the results presented here are limited due to methodological differences across studies. Analysis of these differences is presented and suggestions for future research are offered.

Representation and integration of auditory and visual stimuli in the primate ventral lateral prefrontal cortex

Through the influence of Goldman-Rakic, much research has been focused on the role of the dorsolateral prefrontal cortex in spatial working memory, decision making, and saccade generation, whereas functions of other parts of the frontal lobe including the ventrolateral prefrontal cortex (VLPFC) are less clear. Previous studies in non-human primates have shown that some VLPFC cells are selectively responsive to faces. Recent findings indicate that adjacent to the region where face- and object-selective cells have been recorded are neurons which respond to complex sounds including human and monkey vocalizations. Furthermore, when neurons in this same region are tested with combined face and voice communication stimuli, it is apparent that some cells in VLPFC are multisensory and respond to audiovisual stimuli. The determination that ventral prefrontal neurons are multisensory and responsive to auditory and visual communication stimuli may help to establish an animal model to assist in the investigation of the circuit and cellular basis of human communication. This will also aid in the understanding of general frontal lobe function and the processes that go awry in disorders including autism and schizophrenia, where disturbances in prefrontal function have been noted.

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.

HFA and ADHD: A direct comparison on state regulation and response inhibition

This study examined whether children with high-functioning autism (HFA) are easily overaroused/activated and whether children with attention-deficit/hyperactivity disorder (ADHD) are easily underaroused/activated. This double dissociation was tested using a go/no-go paradigm with computer-paced fast and slow conditions and a self-paced condition. In the HFA group, a performance decline in the fast condition and slow performance in the self-paced condition were expected. In the ADHD group, a performance decline in the slow condition and fast performance in the self-paced condition were expected. No difference was found between groups for state regulation and response inhibition. Findings are discussed in the light of development, comorbidity, and subtypes.

Priming the meaning of homographs in typically developing children and children with autism

Two explanations for deficits underlying autism were tested: weak central coherence (WCC) and executive dysfunction. Consistent with WCC, Happé (British Journal of Developmental Psychology 15 (1997) 1) found that children with autism failed to use sentence context in pronouncing homographs. In an alternate approach, we investigated whether children with autism can use meanings of related word primes. We presented children with autism and controls with primes for homographs, semantically related, and unrelated targets. Children with autism used primes to correctly pronounce homographs upon first presentation but showed difficulty inhibiting prior responses upon later presentation of the homographs with different primes. Children with autism also showed semantic priming effects. We conclude that children with autism do not show an absolute deficit in ability to use contextual information.

Cognitive flexibility in adults with high functioning autism

The goal of the current study was to evaluate presetting, response inhibition, set shifting, and a priori planning in autism: abilities that can be lumped together under the term cognitive flexibility. Cognitive flexibility is an aspect of executive functioning, which in turn is mediated by the prefrontal cortical lobes. A group of adults with high-functioning autism (HFA; n = 23) were compared with a normal control group (n = 32), by using a computerized variant of the Sternberg response bias paradigm. Contrary to the results of earlier studies, no deficit was found in presetting, response inhibition, set shifting, and a priori planning in participants with autism, even when the medication factor was taken into account. Methodological issues that could be explanatory for this difference are discussed. An additional finding was, that individuals with HFA (especially those on medication) were slow in reacting. Possible origins and consequences of this slowness, also for cognitive flexibility, are discussed.

Functional and anatomical cortical underconnectivity in autism: evidence from an FMRI study of an executive function task and corpus callosum morphometry

The brain activation of a group of high-functioning autistic participants was measured using functional magnetic resonance imaging during the performance of a Tower of London task, in comparison with a control group matched with respect to intelligent quotient, age, and gender. The 2 groups generally activated the same cortical areas to similar degrees. However, there were 3 indications of underconnectivity in the group with autism. First, the degree of synchronization (i.e., the functional connectivity or the correlation of the time series of the activation) between the frontal and parietal areas of activation was lower for the autistic than the control participants. Second, relevant parts of the corpus callosum, through which many of the bilaterally activated cortical areas communicate, were smaller in cross-sectional area in the autistic participants. Third, within the autism group but not within the control group, the size of the genu of the corpus callosum was correlated with frontal-parietal functional connectivity. These findings suggest that the neural basis of altered cognition in autism entails a lower degree of integration of information across certain cortical areas resulting from reduced intracortical connectivity. The results add support to a new theory of cortical underconnectivity in autism, which posits a deficit in integration of information at the neural and cognitive levels.

Spatial working memory deficits in autism

Previous studies have reported working memory deficits in autism, but this finding has been inconsistent. One possibility is that deficits in this domain may be present only when working memory load exceeds some limited capacity. High-functioning individuals with autism performed the CANTAB computerized test of spatial working memory. Individuals with autism made more errors than a matched group of typically developing controls on this task, and were less likely to consistently use a specific organized search strategy to complete the task. Overall, these results demonstrate reduced spatial working memory abilities in autism, and extend previous findings by demonstrating that these deficits are significant when tasks impose heavier demands on working memory.

Neuropsychological functioning in adults with Asperger syndrome

There is some consensus in the literature regarding the cognitive profile of people with Asperger syndrome (AS). Findings to date suggest that a proportion of people with AS have higher verbal than performance IQ, a non-verbal learning disability (NVLD) and impairments in some aspects of executive function (EF). However, there are few published studies on adults with AS and many have compared the AS group to an autistic control group alone. We compared cognitive functioning in 27 AS adults without a history of language delay and 20 normal controls who did not differ significantly in age, gender and IQ. People with AS had significant impairments on a test of visual memory and on EF tasks measuring flexibility and generativity, but not inhibition. There was no significant difference between verbal and performance IQ. Our results suggest that impairments on tests requiring flexibility of thought and generation occur at all ages and across a range of autistic disorders including AS.

Deficits in free recall persist in Asperger's syndrome despite training in the use of list-appropriate learning strategies

Free recall in adults with Asperger's Syndrome (AS) was compared with that in matched controls in an experiment including semantically similar, phonologically similar and unrelated word lists. Without supportive instructions, adults with AS were significantly impaired in their recall of phonologically and semantically related lists, but not unrelated lists. Even when trained to make use at study of the relations among the words, the adults with AS recalled fewer words than the control group. Participants rehearsed the study lists out loud and the rehearsal data was analysed. Despite a very slight trend for adults with AS to engage in less elaborative rehearsal and more rote rehearsal, their rehearsal did not differ significantly from that of controls.

The 39,XO mouse as a model for the neurobiology of Turner syndrome and sex-biased neuropsychiatric disorders

Turner syndrome (TS) is a developmental disorder most frequently arising from the loss of a complete X chromosome (karyotype 45,XO). The disorder is characterised by physiological abnormalities (notably short stature and ovarian dysfunction), emotional anomalies (including heightened anxiety) and by a neuropsychological profile encompassing deficits in visuospatial skills, memory, attention, social cognition and emotion recognition. Moreover, TS subjects are at significantly increased risk of developing attention deficit hyperactivity disorder (ADHD) and autism. At the neuroanatomical level, TS subjects display abnormalities across a number of brain structures, including the amygdala, hippocampus and orbitofrontal cortex. The TS phenotype arises due to reduced dosage of X-linked genes, and may also be modulated by parental origin of the single X chromosome. In this review, we discuss the utility of a mouse model of TS, the 39,XO mouse, in which the parental origin of the single X chromosome can be varied. This model provides the opportunity to investigate the effects of X-linked gene dosage/parent-of-origin effects on neurobiology in the absence of gross physiological abnormalities. Initial findings indicate that several features of the TS behavioural phenotype may be accurately recapitulated in the mouse. Furthermore, as X-linked gene dosage/imprinting can influence sex-specific neurobiology, investigations in the 39,XO mouse are also likely to offer insights into why certain neuropsychiatric disorders (including ADHD and autism) affect the sexes differently.

Maturation of executive function in autism

BACKGROUND

Executive dysfunction has been reported at different ages in autism. It is not clear however, when this impairment emerges or how its expression is affected by development.

METHODS

61 non-mentally retarded autism participants (AUT) and 61 age, gender, and IQ matched typically developing participants (CON) were assessed with two oculomotor executive function tasks, the oculomotor delayed response task (ODR) and the antisaccade task (AS), as well as a visually-guided saccade sensorimotor task (VGS).

RESULTS

The AUT group demonstrated impairments in response inhibition and spatial working memory at all ages tested. Developmental improvements in speed of sensorimotor processing and voluntary response inhibition were similar in both groups indicating sparing of some attentional control of behavior. Developmental progression in the speed of initiating a cognitive plan and maintaining information on line over time, however, was impaired in the AUT group indicating abnormal development of working memory.

CONCLUSIONS

These results indicate that while executive dysfunction is present throughout development, there is evidence for both typical and atypical developmental progression of executive functions in autism. The plasticity suggested by the developmental improvements may have implications regarding appropriate developmental epochs and types of interventions aimed at enhancing cognitive capacities in individuals with autism.

Supported employment improves cognitive performance in adults with Autism

BACKGROUND

The purpose of this study was to examine the effects of a supported employment programme on measures of executive functions for 44 adults with autism, assessed at the beginning and the end of the programme period. The average length of time of the community employment was 30 months.

METHODS

Based on their predominant work activity over the study period, participants were classified into two groups: supported employment and unemployed. At the start of the programme, the groups did not differ on any of the cognitive measures.

RESULTS

Repeated measures analysis of variance (anova) demonstrated that by the end of the programme, the supported employment group showed higher scores for executive functions on variables of CANTAB (Spatial Span Task--span length recalled; Spatial Working Memory Task--strategy; Planning task 'Stockings of Cambridge'--problems solved in minimum moves; Planning task 'Stockings of Cambridge'--mean planning time) and other tasks such as Trail Making Test - part B, time; Matching Familiar Figures (first answer and errors). In contrast, the unemployed group showed no change over time in their cognitive performance.

CONCLUSION

Results of this study suggested that vocational rehabilitation programmes have a beneficial impact upon cognitive performance in people with autism.

Social stimuli interfere with cognitive control in autism

Autism spectrum disorders are characterized by cognitive control deficits as well as impairments in social interactions. However, the brain mechanisms mediating the interactive effects of these deficits have not been addressed. We employed event-related functional magnetic resonance imaging (fMRI) to examine the effects of processing directional information from faces on activity within brain regions mediating cognitive control. High-functioning individuals with autism and age-, gender-, and IQ-matched neurotypical individuals attended to the direction of a centrally-presented arrow or gaze stimulus with similar flanker stimuli oriented in the same ("congruent") or opposite ("incongruent") direction. The incongruent arrow condition was examined to assess functioning of brain regions mediating cognitive control in a context without social-cognitive demands, whereas the incongruent gaze condition assessed functioning of the same brain regions in a social-cognitive context. Consistent with prior studies, the incongruent arrow condition recruited activity in bilateral midfrontal gyrus, right inferior frontal gyrus, bilateral intraparietal sulcus, and the anterior cingulate relative to the congruent arrow condition in neurotypical participants. Notably, there were not diagnostic group differences in patterns of regional fMRI activation in response to the arrow condition. However, while viewing the incongruent gaze stimuli, although neurotypical participants recruited the same brain regions, participants with autism showed marked hypoactivation in these areas. These findings suggest that processing social-cognitive stimuli interferes with functioning of brain regions recruited during cognitive control tasks in autism. Implications for research into cognitive control deficits in autism are discussed.

Post-error adaptation in adults with high functioning autism

Deficits in executive function (EF), i.e. function of the prefrontal cortex, may be central in the etiology of autism. One of the various aspects of EF is error detection and adjusting behavior after an error. In cognitive tests, adults normally slow down their responding on the next trial after making an error, a compensatory mechanism geared toward improving performance on subsequent trials, and a faculty critically associated with activity in the anterior cingulate cortex (ACC). The current study evaluated post-error slowing in people with high functioning autism (HFA) (n=36), taking symptom severity into account, compared to the performance of a normal control group (n=32). Symptom severity in the HFA group was defined in terms of level of adaptation: living independently (outpatients; n=12) and living residentially (inpatients; n=24). Half the group of inpatients was on medication; the results of their performance were analyzed separately. A computerized version of a memory search task was used with two response probability conditions. The subjects in the control group adjusted their reaction time (RT) substantially after an error, while the group of participants with HFA appeared to be overall slow, with no significant adjustment of RT after an error. This finding remained significant if the medication factor was taken into account, and was independent of the degree of severity of the autistic disorder, as defined by the dichotomy 'inpatient versus outpatient'. Possible causes and implications of the finding are discussed.

Introducing MASC: a movie for the assessment of social cognition

In the present study we introduce a sensitive video-based test for the evaluation of subtle mindreading difficulties: the Movie for the Assessment of Social Cognition (MASC). This new mindreading tool involves watching a short film and answering questions referring to the actors' mental states. A group of adults with Asperger syndrome (n = 19) and well-matched control subjects (n = 20) were administered the MASC and three other mindreading tools as part of a broader neuropsychological testing session. Compared to control subjects, Asperger individuals exhibited marked and selective difficulties in social cognition. A Receiver Operating Characteristic (ROC) analysis for the mindreading tests identified the MASC as discriminating the diagnostic groups most accurately. Issues pertaining to the multidimensionality of the social cognition construct are discussed.

Imitation of Intentional and Accidental Actions by Children with Autism

To determine whether children with autism (CWA) would selectively imitate intentional, as opposed to accidental actions, an experimenter demonstrated either an "intentional" and an "accidental" action or two "intentional" actions on the same toy [Carpenter, Akhtar, & Tomasello (1998a) Infant Behavior and Development, 21, 315-330]. CWA tended to imitate the experimenter exactly. Children with developmental delay and older typically developing children (TD) reproduced only the intentional action as often as they imitated the experimenter exactly. Younger TD mostly produced only the intentional action. It is concluded that, contrary to comparison groups, the CWA did not show an appreciation of the model's intentions. Results are discussed in terms of theories of social cognition.