Evidence for executive dysfunction in autism

Reduced behavioral flexibility in autism spectrum disorders

OBJECTIVE

Restricted and repetitive behaviors, and a pronounced preference for behavioral and environmental consistency, are distinctive characteristics of autism spectrum disorders (ASD). Whether these clinical features of ASD are related to fundamental neuropsychological impairments in behavioral flexibility remains to be clarified.

METHOD

Forty-one individuals with ASD and 37 matched controls performed a probabilistic reversal learning task to assess behavioral flexibility. Participants learned to choose the correct stimulus location from a pair of locations to win points (acquisition). After making the correct choice over multiple trials, the rewarded stimulus location changed without warning (reversal). Feedback was provided on an 80:20 probabilistic schedule, with 80% of correct choices and 20% of incorrect choices randomly reinforced.

RESULTS

ASD and control participants performed comparably during acquisition. At reversal, ASD participants initially chose the new correct location as quickly as controls, but then more frequently reverted back to the previously preferred response. The ASD group also more frequently shifted back to the previous response choice immediately following intermittent non-reinforcement of the new correct response. The number of regressive errors was positively correlated with independently ascertained clinical ratings of restricted and repetitive behaviors, but not other core features of ASD.

CONCLUSIONS

Restricted and repetitive behaviors in ASD are associated with neurocognitive deficits in flexible choice behavior. Preclinical research has established that frontostriatal circuitry supports flexibility on reversal learning tasks. Thus, alterations in this circuitry may contribute to behavioral rigidity in ASD and represent a target for therapeutic intervention.

Is EEG-biofeedback an effective treatment in autism spectrum disorders? A randomized controlled trial

EEG-biofeedback has been reported to reduce symptoms of autism spectrum disorders (ASD) in several studies. However, these studies did not control for nonspecific effects of EEG-biofeedback and did not distinguish between participants who succeeded in influencing their own EEG activity and participants who did not. To overcome these methodological shortcomings, this study evaluated the effects of EEG-biofeedback in ASD in a randomized pretest-posttest control group design with blinded active comparator and six months follow-up. Thirty-eight participants were randomly allocated to the EEG-biofeedback, skin conductance (SC)-biofeedback or waiting list group. EEG- and SC-biofeedback sessions were similar and participants were blinded to the type of feedback they received. Assessments pre-treatment, post-treatment, and after 6 months included parent ratings of symptoms of ASD, executive function tasks, and 19-channel EEG recordings. Fifty-four percent of the participants significantly reduced delta and/or theta power during EEG-biofeedback sessions and were identified as EEG-regulators. In these EEG-regulators, no statistically significant reductions of symptoms of ASD were observed, but they showed significant improvement in cognitive flexibility as compared to participants who managed to regulate SC. EEG-biofeedback seems to be an applicable tool to regulate EEG activity and has specific effects on cognitive flexibility, but it did not result in significant reductions in symptoms of ASD. An important finding was that no nonspecific effects of EEG-biofeedback were demonstrated.

Autism, processing speed, and adaptive functioning in preschool children

Objectives. To study cognitive test profiles with a focus on processing speed in a representative group of preschool children with autism spectrum disorder (ASD) and relate processing speed to adaptive functioning. Methods. Cognitive assessments were performed in 190 3.6–6.6-year-old children (164 boys and 26 girls) with ASD, using either Griffiths' developmental scales (n = 77) or the Wechsler Preschool and Primary Scale of Intelligence-Third Edition (WPPSI-III) (n = 113). Cognitive data were related to adaptive functioning as measured by Vineland Adaptive Behavior Scales (VABS). Results. Cognitive profiles were characterized by low verbal skills. Low processing speed quotients (PSQs) were found in 66 (78%) of the 85 children who were able to participate in the processing speed subtests. Except for Socialization, all VABS domains (Communication, Motor Skills, Daily Living Skills, and Adaptive Behavior Composite scores) correlated significantly with PSQ. Multiple regression analysis showed that PSQ predicted 38%, 35%, 34%, and 37% of the variance for Communication, Daily Living Skills, Motor Skills, and total Adaptive Composite scores, respectively. Conclusion. Preschool children with ASD had uneven cognitive profiles with low verbal skills, and, relatively, even lower PSQs. Except for Socialization, adaptive functioning was predicted to a considerable degree by PSQ.

Altered modular organization of structural cortical networks in children with autism

Autism is a complex developmental disability that characterized by deficits in social interaction, language skills, repetitive stereotyped behaviors and restricted interests. Although great heterogeneity exists, previous findings suggest that autism has atypical brain connectivity patterns and disrupted small-world network properties. However, the organizational alterations in the autistic brain network are still poorly understood. We explored possible organizational alterations of 49 autistic children and 51 typically developing controls, by investigating their brain network metrics that are constructed upon cortical thickness correlations. Three modules were identified in controls, including cortical regions associated with brain functions of executive strategic, spatial/auditory/visual, and self-reference/episodic memory. There are also three modules found in autistic children with similar patterns. Compared with controls, autism demonstrates significantly reduced gross network modularity, and a larger number of inter-module connections. However, the autistic brain network demonstrates increased intra- and inter-module connectivity in brain regions including middle frontal gyrus, inferior parietal gyrus, and cingulate, suggesting one underlying compensatory mechanism associated with brain functions of self-reference and episodic memory. Results also show that there is increased correlation strength between regions inside frontal lobe, as well as impaired correlation strength between frontotemporal and frontoparietal regions. This alteration of correlation strength may contribute to the organization alteration of network structures in autistic brains.

Do adults with autism spectrum disorders compensate in naturalistic prospective memory tasks?

The present study is the first to directly compare event- and time-based prospective memory in Autism Spectrum Disorders (ASD) using a contextual task mirroring real life demands of prospective memory. Twenty-five individuals with ASD and 25 age- and ability-matched controls completed the Dresden Breakfast task which required participants to prepare breakfast following a set of rules and time restrictions. Overall, adults with ASD had less correct time- and event-based prospective memory responses in comparison to controls, which is consistent with previous research in children with ASD. Moreover, ASD participants completed fewer tasks, followed rules less closely, and monitored the elapsing time less closely than controls. Individuals with ASD seem not to be compensating in naturalistic prospective memory tasks.

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.

A review of intentional and cognitive control in autism

Different clinical studies have provided empirical evidence for impairments in cognitive control in individuals with autism spectrum disorders (ASD). The challenge arises, however, when trying to specify the neurocognitive mechanisms behind the reported observations of deviant patterns of goal-directed behavior in ASD. Studies trying to test specific assumptions by applying designs that are based on a more controlled experimental conditions often fail in providing strong evidence for an impairment in specific cognitive functions. In this review, we summarize and critically reflect on behavioral findings and their theoretical explanations regarding cognitive control processing in autism, also from a developmental perspective. The specific focus of this review is the recent evidence of deficits in intentional control – a specific subset of cognitive control processes that biases the choice of our behavioral goals – coming from different research fields. We relate this evidence to the cognitive rigidity observed in ASD and argue that individuals with ASD experience problems at the intentional level rather than at the level of implementation of intentions. Both these processes are related to cognitive control mechanisms but in different ways. Finally, we discuss new directions in studying cognitive control in ASD and how these relate to adaptive cognition.

Cognition in males and females with autism: similarities and differences

The male bias in autism spectrum conditions (ASC) has led to females with ASC being under-researched. This lack of attention to females could hide variability due to sex that may explain some of the heterogeneity within ASC. In this study we investigate four key cognitive domains (mentalizing and emotion perception, executive function, perceptual attention to detail, and motor function) in ASC, to test for similarities and differences between males and females with and without ASC (n = 128 adults; n = 32 per group). In the mentalizing and facial emotion perception domain, males and females with ASC showed similar deficits compared to neurotypical controls. However, in attention to detail and dexterity involving executive function, although males with ASC showed poorer performance relative to neurotypical males, females with ASC performed comparably to neurotypical females. We conclude that performance in the social-cognitive domain is equally impaired in male and female adults with ASC. However, in specific non-social cognitive domains, performance within ASC depends on sex. This suggests that in specific domains, cognitive profiles in ASC are modulated by sex.

Cross-modal attention-switching is impaired in autism spectrum disorders

This investigation aimed to determine if children with ASD are impaired in their ability to switch attention between different tasks, and whether performance is further impaired when required to switch across two separate modalities (visual and auditory). Eighteen children with ASD (9-13 years old) were compared with 18 typically-developing children matched with the ASD group for mental age, and also with 18 subjects with learning difficulties matched with the ASD group for mental and chronological age. Individuals alternated between two different visual tasks, and between a different visual task and an auditory task. Children with ASD performed worse than both comparison groups at both switching tasks. Moreover, children with ASD had greater difficulty when different modalities were required than where only one modality was required in the switching task in comparison with participants matched in terms of mental and chronological age.

Far from action-blind: Representation of others' actions in individuals with Autism

It has been suggested that theory of mind may rely on several precursors including gaze processing, joint attention, the ability to distinguish between actions of oneself and others, and the ability to represent goal-directed actions. Some of these processes have been shown to be impaired in individuals with autism, who experience difficulties in theory of mind. However, little is known about action representation in autism. Using two variants of a spatial compatibility reaction time (RT) task, we addressed the question of whether high-functioning individuals with autism have difficulties in controlling their own actions and in representing those of others. Participants with autism showed automatic response activation and had no difficulties with response inhibition. When two action alternatives were distributed among pairs of participants, participants with autism represented a co-actor's task, showing the same pattern of results as the matched control group. We discuss the possibility that in high-functioning individuals with autism, the system matching observed actions onto representations of one's own actions is intact, whereas difficulties in higher-level processing of social information persist.

Visual Scanning Patterns during the Dimensional Change Card Sorting Task in Children with Autism Spectrum Disorder

Impaired cognitive flexibility in children with autism spectrum disorder (ASD) has been reported in previous literature. The present study explored ASD children's visual scanning patterns during the Dimensional Change Card Sorting (DCCS) task using eye-tracking technique. ASD and typical developing (TD) children completed the standardized DCCS procedure on the computer while their eye movements were tracked. Behavioral results confirmed previous findings on ASD children's deficits in executive function. ASD children's visual scanning patterns also showed some specific underlying processes in the DCCS task compared to TD children. For example, ASD children looked shorter at the correct card in the postswitch phase and spent longer time at blank areas than TD children did. ASD children did not show a bias to the color dimension as TD children did. The correlations between the behavioral performance and eye moments were also discussed.

Differences in white matter reflect atypical developmental trajectory in autism: A Tract-based Spatial Statistics study

Autism is a neurodevelopmental disorder in which white matter (WM) maturation is affected. We assessed WM integrity in 16 adolescents and 14 adults with high-functioning autism spectrum disorder (ASD) and in matched neurotypical controls (NT) using diffusion weighted imaging and Tract-based Spatial Statistics. Decreased fractional anisotropy (FA) was observed in adolescents with ASD in tracts involved in emotional face processing, language, and executive functioning, including the inferior fronto-occipital fasciculus and the inferior and superior longitudinal fasciculi. Remarkably, no differences in FA were observed between ASD and NT adults.

We evaluated the effect of age on WM development across the entire age range. Positive correlations between FA values and age were observed in the right inferior fronto-occipital fasciculus, the left superior longitudinal fasciculus, the corpus callosum, and the cortical spinal tract of ASD participants, but not in NT participants.

Our data underscore the dynamic nature of brain development in ASD, showing the presence of an atypical process of WM maturation, that appears to normalize over time and could be at the basis of behavioral improvements often observed in high-functioning autism.

Relationship between reaction time, fine motor control, and visual-spatial perception on vigilance and visual-motor tasks in 22q11.2 Deletion Syndrome

22q11.2 Deletion Syndrome (22q11DS) is a common microdeletion disorder associated with mild to moderate intellectual disability and specific neurocognitive deficits, particularly in visual-motor and attentional abilities. Currently there is evidence that the visual-motor profile of 22q11DS is not entirely mediated by intellectual disability and that these individuals have specific deficits in visual-motor integration. However, the extent to which attentional deficits, such as vigilance, influence impairments on visual motor tasks in 22q11DS is unclear. This study examines visual-motor abilities and reaction time using a range of standardised tests in 35 children with 22q11DS, 26 age-matched typically developing (TD) sibling controls and 17 low-IQ community controls. Statistically significant deficits were observed in the 22q11DS group compared to both low-IQ and TD control groups on a timed fine motor control and accuracy task. The 22q11DS group performed significantly better than the low-IQ control group on an untimed drawing task and were equivalent to the TD control group on point accuracy and simple reaction time tests. Results suggest that visual motor deficits in 22q11DS are primarily attributable to deficits in psychomotor speed which becomes apparent when tasks are timed versus untimed. Moreover, the integration of visual and motor information may be intact and, indeed, represent a relative strength in 22q11DS when there are no time constraints imposed. While this may have significant implications for cognitive remediation strategies for children with 22q11DS, the relationship between reaction time, visual reasoning, cognitive complexity, fine motor speed and accuracy, and graphomotor ability on visual-motor tasks is still unclear.

Computerized neuropsychological testing to rapidly evaluate cognition in pediatric patients with neurologic disorders

Computerized neuropsychological tests represent a viable method for rapidly screening cognition. The purpose of this study was to explore performance on the CNS Vital Signs in a large pediatric neurology sample. Participants included 166 neurology patients (mean age, 13.0 years; standard deviation, 3.2) and 281 controls (mean age, 13.2 years; standard deviation, 3.2) between 7 and 19 years. The neurology sample performed significantly worse on all domain scores and nearly all subtest scores. Cohen d effect sizes were small to medium for verbal memory (d= 0.44), visual memory (d= 0.40), and reaction time (d= 0.48) and very large for psychomotor speed (d= 1.19), complex attention (d = 0.94), cognitive flexibility (d = 0.94), and the overall composite score (d = 1.08). Using the criterion for cognitive impairment of 2 or more scores ≤5th percentile, 36.6% of the neurology sample was identified as having an uncommon cognitive profile. This is the first study to demonstrate the performance of pediatric patients with neurologic disorders on CNS Vital Signs.

The development of executive function in autism

Autism is a common and often highly debilitating neurodevelopmental condition, whose core behavioral features are believed to be rooted in disrupted neurocognitive processes, including especially "executive function." Researchers have predominantly focused upon understanding the putative causal relationship between difficulties in EF and autistic symptomatology. This paper suggests, however, that the effects of individual differences in EF should be more far-reaching, playing a significant part in the real-life outcomes of individuals with autism, including their social competence, everyday adaptive behavior, and academic achievement. It further considers the nature of the EF-outcome relationship, including the possible determinants of individual differences in EF, and makes several recommendations for future research.

Relationship between executive functions and motor stereotypies in children with Autistic Disorder

This study reports on the relationship between motor stereotypies and impairments in executive functions (EF) in children with Autistic Disorder (AD) and in children with Developmental Language Disorders (DLD). We hypothesized that low EF performance would predict higher frequency and longer durations of stereotypies in the AD group only. Twenty-two children (age range = 7-9 years, 6 months, girls = 5) with AD were recruited from a longitudinal multi-site study and compared to twenty-two non-autistic children with DLD (age range = 7-9 years, 6 months, girls = 5). The two groups were matched on non-verbal IQ and demographic characteristics. Frequency and duration of stereotypies were coded from videotaped semi-structured play sessions. EF measures included the Wisconsin Card Sorting Task (WCST) Categories, Wechsler Intelligence Scale for Children-Revised (WISC-R) Mazes, and Stanford-Binet Fourth Edition (SB-IV) Matrices. The scores for frequency and duration of stereotypies were higher in the AD group. Separate linear regressions revealed that group status, EF, and their interactions predict stereotypies. Specifically, lower EF scores predicted higher frequencies and longer durations of stereotypies in the AD group only. Analyses controlled for age, gender, and parent education. Findings suggest that in AD, EF impairments and stereotypies may be linked to shared brain pathways.

Executive functions of six-year-old boys with normal birth weight and gestational age

Impaired fetal development, reflected by low birth weight or prematurity, predicts an increased risk for psychopathology, especially attention deficit hyperactivity disorder (ADHD). Such effects cut across the normal range of birth weight and gestation. Despite the strength of existing epidemiological data, cognitive pathways that link fetal development to mental health are largely unknown. In this study we examined the relation of birth weight (>2500 g) and gestational age (37-41 weeks) within the normal range with specific executive functions in 195 Singaporean six-year-old boys of Chinese ethnicity. Birth weight adjusted for gestational age was used as indicator of fetal growth while gestational age was indicative of fetal maturity. Linear regression revealed that increased fetal growth within the normal range is associated with an improved ability to learn rules during the intra/extra-dimensional shift task and to retain visual information for short period of time during the delayed matching to sample task. Moreover, faster and consistent reaction times during the stop-signal task were observed among boys born at term, but with higher gestational age. Hence, even among boys born at term with normal birth weight, variations in fetal growth and maturity showed distinct effects on specific executive functions.

Autism as a neural systems disorder: a theory of frontal-posterior underconnectivity

The underconnectivity theory of autism attributes the disorder to lower anatomical and functional systems connectivity between frontal and more posterior cortical processing. Here we review evidence for the theory and present a computational model of an executive functioning task (Tower of London) implementing the assumptions of underconnectivity. We make two modifications to a previous computational account of performance and brain activity in typical individuals in the Tower of London task (Newman et al., 2003): (1) the communication bandwidth between frontal and parietal areas was decreased and (2) the posterior centers were endowed with more executive capability (i.e., more autonomy, an adaptation is proposed to arise in response to the lowered frontal-posterior bandwidth). The autism model succeeds in matching the lower frontal-posterior functional connectivity (lower synchronization of activation) seen in fMRI data, as well as providing insight into behavioral response time results. The theory provides a unified account of how a neural dysfunction can produce a neural systems disorder and a psychological disorder with the widespread and diverse symptoms of autism.

Flexibility in children with autism spectrum disorders (ASD): inconsistency between neuropsychological tests and parent-based rating scales

In this study, we compared neuropsychological tests and parent-based ratings of flexibility in a sample of children with autism spectrum disorders (ASD). We investigated the discriminant validity of the domain-specific flexibility measures by comparison with the domain general measures, general behavioral problems, general ASD-related traits, and general intelligence. Tests and parent-based ratings of flexibility were not significantly correlated. Parent-based ratings were strongly related with the three broadband measures, whereas the discriminant validity indices of the neuropsychological tests were satisfactory. These findings suggest that parent-based ratings do not reflect the specific executive construct of flexibility, but instead reflect a broad spectrum of general child characteristics.

Animal models of neuropsychiatry revisited: a personal tribute to Teitelbaum

Several themes and principles of behavioural neuroscience are evident in the work of Phillip Teitelbaum. He has emphasised the importance of studying behaviour in simple preparations, of re-synthesising complex behavioural patterns from these elemental 'building-blocks' and understanding their often hierarchical organisation. He also more recently has become interested in the possible power of behavioural endophenotypes. His work has resulted in a new emphasis on animal neuropsychology which is highly relevant to human psychopathology. This article illustrates these themes from examples taken from animal models of sensory neglect, drug addiction and cognitive syndromes associated with schizophrenia and other neuropsychiatric disorders.

Sensory Differences and Stereotyped Movements in Children with Autism

This study was designed to test whether there is a functional relationship between sensory stimulation and stereotyped movements (SM). Four children with autism and intellectual disability (according to DSM-IV criteria) who showed stereotyped movements were studied. The Short Sensory Profile was used to define whether a child perceived stimulation within each sensory modality as aversive, attractive, or neutral. The Stereotyped and Self-Injurious Movements Interview was used to identify each child's repetitive movements. Children were then exposed to sensory stimuli that were neutral, aversive or attractive. Results indicate that children: (a) initiate or increase stereotyped movements immediately following the onset of an aversive stimulus, (b) terminate or decrease stereotyped movements following the onset of an attractive stimulus and (c) initiate or increase stereotyped movements during periods of neutral stimulation. We conclude that stereotyped movements are functionally related to sensory stimulation; individuals who frequently engage in stereotyped movements may do so in order to cope with under-stimulation and aversive over-stimulation.

Time-Based Prospective Memory in Children With Autism Spectrum Disorder

In this study, for the first time, prospective memory was investigated in 11 school-aged children with autism spectrum disorders and 11 matched neurotypical controls. A computerised time-based prospective memory task was embedded in a visuospatial working memory test and required participants to remember to respond to certain target times. Controls had significantly more correct prospective memory responses than the autism spectrum group. Moreover, controls checked the time more often and increased time-monitoring more steeply as the target times approached. These differences in time-checking may suggest that prospective memory in autism spectrum disorders is affected by reduced self-initiated processing as indicated by reduced task monitoring.

Are executive control functions related to autism symptoms in high-functioning children?

BACKGROUND

Linking autism symptoms to cognitive abilities can expand phenotypic descriptions and facilitate investigations into the etiology and treatment of this multiplex disorder. Executive dysfunction is one of several potential cognitive phenotypes in autism.

METHOD

Archival clinical data on 89 children diagnosed with Autism Spectrum Disorders and administered a large neuropsychological battery were evaluated for relationships between executive functioning and autism symptoms.

RESULTS

Significant relationships between both laboratory tasks and behavior rating scales of executive functions and autism symptoms were identified. Multiple regression analyses revealed that measures of semantic fluency, divided auditory attention, and behavioral regulation were significantly correlated with autism symptoms, even after accounting for the variance from correlated "nuisance variables," such as vocabulary and age.

CONCLUSIONS

Executive dysfunction is related to all three clusters of behavioral symptoms in Autism Spectrum Disorders.

Differences in BTBR T+ tf/J and C57BL/6J mice on probabilistic reversal learning and stereotyped behaviors

Autism spectrum disorders (ASD) represent a class of neurodevelopmental disorders characterized by impairments in social interaction, verbal and non-verbal communication, as well as restricted interests and repetitive behavior. This latter class of symptoms often includes features such as compulsive behaviors and resistance to change. The BTBR T+ tf/J mouse strain has been used as an animal model to investigate the social communication and restricted interest features in ASD. Less is known about whether this mouse strain models cognitive flexibility deficits also observed in ASD. The present experiment investigated performance of BTBR T+ tf/J and C57BL/6J on two different spatial reversal learning tests (100% accurate feedback and 80/20 probabilistic feedback), as well as marble burying and grooming behavior. BTBR T+ tf/J and C57BL/6J mice exhibited similar performance on acquisition and reversal learning with 100% accurate feedback. BTBR T+ tf/J mice were impaired in probabilistic reversal learning compared to that of C57BL/6J mice. BTBR T+ tf/J mice also displayed increased stereotyped repetitive behaviors compared to that of C57BL/6J mice as shown by increased marble burying and grooming behavior. The present findings indicate that BTBR T+ tf/J mice exhibit similar features related to "insistence on sameness" in ASD that include not only stereotyped repetitive behaviors, but also alterations in behavioral flexibility. Thus, BTBR T+ tf/J mice can serve as a model to understand the neural mechanisms underlying alterations in behavioral flexibility, as well as to test potential treatments in alleviating these symptoms.

Disrupted cortical connectivity theory as an explanatory model for autism spectrum disorders

Recent findings of neurological functioning in autism spectrum disorder (ASD) point to altered brain connectivity as a key feature of its pathophysiology. The cortical underconnectivity theory of ASD (Just et al., 2004) provides an integrated framework for addressing these new findings. This theory suggests that weaker functional connections among brain areas in those with ASD hamper their ability to accomplish complex cognitive and social tasks successfully. We will discuss this theory, but will modify the term underconnectivity to 'disrupted cortical connectivity' to capture patterns of both under- and over-connectivity in the brain. In this paper, we will review the existing literature on ASD to marshal supporting evidence for hypotheses formulated on the disrupted cortical connectivity theory. These hypotheses are: 1) underconnectivity in ASD is manifested mainly in long-distance cortical as well as subcortical connections rather than in short-distance cortical connections; 2) underconnectivity in ASD is manifested only in complex cognitive and social functions and not in low-level sensory and perceptual tasks; 3) functional underconnectivity in ASD may be the result of underlying anatomical abnormalities, such as problems in the integrity of white matter; 4) the ASD brain adapts to underconnectivity through compensatory strategies such as overconnectivity mainly in frontal and in posterior brain areas. This may be manifested as deficits in tasks that require frontal-parietal integration. While overconnectivity can be tested by examining the cortical minicolumn organization, long-distance underconnectivity can be tested by cognitively demanding tasks; and 5) functional underconnectivity in brain areas in ASD will be seen not only during complex tasks but also during task-free resting states. We will also discuss some empirical predictions that can be tested in future studies, such as: 1) how disrupted connectivity relates to cognitive impairments in skills such as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD.

Stereotyped behaviour in children with autism and intellectual disability: an examination of the executive dysfunction hypothesis

BACKGROUND

Increasing attention has been paid to the executive dysfunction hypothesis argued to underpin stereotyped behaviour in autism. The aim of this study is to investigate one component of this model, that stereotyped behaviours are related to impaired generativity and compromised behavioural inhibition, by examining whether episodes of these behaviours terminate naturally without external intervention.

METHODS

Using a naturalistic observational methodology the stereotyped behaviours of six participants with autism were recorded in real time over periods ranging from 3.59 to 9.20 h. Data were also recorded for teaching staff interactions with participants and environmental settings (one-to-one, group and freetime).

RESULTS

In comparison with one-to-one settings stereotyped behaviours were more frequent when participants were in freetime settings with the exception of one participant. For the termination of stereotyped behaviours these behaviours stopped with no ongoing physical or verbal adult contact being evident for a median of 73.25% of the time. Additionally, for a median of 89.40% of the time stereotyped behaviour stopped without the initiation of adult contact.

DISCUSSION

The termination of bouts of stereotyped behaviour was frequently not associated with any adult contact and thus this form of external intervention. This finding warrants explanation by extending the hypothesis that compromised impaired generativity and behavioural inhibition offers a complete explanation of stereotyped behaviours.

Flexibility in young people with autism spectrum disorders on a card sort task

Adults with autism spectrum disorders (ASD) have shown deficits in switching between rules governing their behaviour, as have high-functioning children with ASD. However, there are few studies of flexibility in lower-functioning children with ASD. The current study investigated this phenomenon with a group of low-functioning children with ASD compared to a mental-age-matched comparison group. The ASD group learned an initial discrimination task as quickly as the matched comparison group, but when the rule governing the discrimination was shifted, the comparison group learned the task with fewer errors, and made the discrimination more quickly than the groups with ASD. These findings suggest that low-functioning children with ASD do display the predicted deficits in extra-dimensional shift.

Partial occlusion depiction and its relationship with field independence in children with ASD

We report a study of the depiction of partial occlusion and its relationship with field independence (FI) in children with ASD. Nineteen ASD children and 29 TD children (5;6-10;0) attempted to copy two 3D occluded scenes, and also selected the 'best' depiction of these scenes in drawings by others. ASD children were not significantly different from controls on FI but were significantly delayed in partial occlusion drawing and selection, independently of chronological age (CA), nonverbal mental age (NVMA) and FI. The results suggest that the depiction of partial occlusion in children with ASD is not qualitatively distinct from that in children with typical development but is significantly and specifically delayed.

In vivo 1H-magnetic resonance spectroscopy study of the attentional networks in autism

Attentional dysfunction is one of the most consistent findings in individuals with autism spectrum disorders (ASD). However, the significance of such findings for the pathophysiology of autism is unclear. In this study, we investigated cellular neurochemistry with proton magnetic resonance spectroscopy imaging ((1)H-MRS) in brain regions associated with networks subserving alerting, orienting, and executive control of attention in patients with ASD. Concentrations of cerebral N-acetyl-aspartate (NAA), creatinine+phosphocreatinine, choline-containing compounds, myo-inositol (Ins) and glutamate+glutamine (Glx) were determined by 3T (1)H-MRS examinations in 14 high-functioning medication-free adults with a diagnosis of ASD and 14 age- and IQ-matched healthy controls (HC) in the anterior cingulate cortex (ACC), thalamus, temporoparietal junction (TPJ), and areas near or along the intraparietal sulcus (IPS). Compared to HC group, the ASD group showed significantly lower Glx concentration in right ACC and reduced Ins concentration in left TPJ. This study provides evidence of abnormalities in neurotransmission related to networks subserving executive control and alerting of attention, functions which have been previously implicated in ASD pathogenesis.

Behavioral flexibility in a mouse model of developmental cerebellar Purkinje cell loss

Although behavioral inflexibility and Purkinje cell loss are both well established in autism, it is unknown if these phenomena are causally related. Using a mouse model, we tested the hypothesis that developmental abnormalities of the cerebellum, including Purkinje cell loss, result in behavioral inflexibility. Specifically, we made aggregation chimeras (Lc/+<-->+/+) between lurcher (Lc/+) mutant embryos and wildtype (+/+) control embryos. Lurcher mice lose 100% of their Purkinje cells postnatally, while chimeric mice lose varying numbers of Purkinje cells. We tested these mice on the acquisition and serial reversals of an operant conditional visual discrimination, a test of behavioral flexibility in rodents. During reversals 1 and 2, all groups of mice committed similar numbers of "perseverative" errors (those committed while session performance was <= 40% correct). Lurchers, however, committed a significantly greater number of "learning" errors (those committed while session performance was between 41% and 85% correct) than both controls and chimeras, and most were unable to advance past reversal 3. During reversals 3 and 4, chimeras, as a group, committed more "perseverative", but not "learning" errors than controls, although a comparison of Purkinje cell number and performance in individual mice revealed that chimeras with fewer Purkinje cells made more "learning" errors and had shorter response latencies than chimeras with more Purkinje cells. These data suggest that developmental cerebellar Purkinje cell loss may affect higher level cognitive processes which have previously been shown to be mediated by the prefrontal cortex, and are commonly deficient in autism spectrum disorders.

Performance of children with autism spectrum disorders on the dimension-change card sort task

Restricted and repetitive behaviors in autism spectrum disorders have been conceptualized to reflect impaired executive functions. In the present study, we investigated the performance of 6-17-year-old children with and without an autism spectrum disorder on a dimension-change card sort task that explicitly indicated sorting rules on every trial. Diagnostic groups did not differ in speed of responses after the first rule switch or in speed or accuracy on blocks with mixed versus single sort rules. However, performance of the ASD group was significantly slower and less accurate overall than the typically-developing group. Furthermore, within the ASD group, poorer DCCS task performance did not predict more severe autism symptoms. Implications for the executive dysfunction theory of autism are discussed.

Tracking executive function across the transition to school: a latent variable approach

This longitudinal study of executive function (EF) addressed three questions. These concerned: (i) the validity of EF as a latent construct underpinning performance at ages 4 and 6 on tests of planning, inhibitory control, and working memory; (ii) developmental change in EF across these time-points, which straddled children's transition to school; and (iii) verbal ability and family income as predictors of base-line individual differences and variation in the slopes of EF development. Confirmatory factor analyses of data from a socially diverse sample of 191 children supported the validity of a single EF construct at both time-points; a MIMIC (multiple indicators, multiple causes) model showed equally good fit for boys and girls. Latent growth models demonstrated that verbal mental age and family income predicted EF intercepts, but EF slopes were only related to verbal mental age. Across the transition to school, less able children (but not children from low income families) showed greater gains in EF than their peers.

Dorsolateral prefrontal cortex magnetic resonance imaging measurements and cognitive performance in autism

This study examined the relationships between volumetric measurements of frontal lobe structures and performance on executive function tasks in individuals with autism. Magnetic resonance imaging (MRI) scans were obtained from 38 individuals with autism and 40 matched controls between the ages of 8 and 45 years. Executive function was assessed using neuropsychological measures including the Wisconsin Card Sorting Test and Tower of Hanoi. Differences in performance on the neuropsychological tests were found between the 2 groups. However, no differences in dorsolateral prefrontal cortex volumes were observed between groups. No correlations between volumetric measurements and performance on the neuropsychological tests were found. Findings from this study suggest that executive function deficits observed in autism are related to functional but not anatomical abnormalities of the frontal lobe. The absence of correlations suggests that executive dysfunction is not the result of focal brain alterations but, rather, is the result of a distributed neural network dysfunction.

Visuospatial short-term memory explains deficits in tower task planning in high-functioning children with autism spectrum disorder

Previous findings on planning abilities in individuals with high-functioning autism spectrum disorder (HFA) are inconsistent. Exploring possible reasons for these mixed findings, the current study investigated the involvement of memory in planning performance in 15 children with HFA and 17 typically developing controls. In addition to planning abilities (measured with the Tower of London), short-term memory and delayed recall for verbal as well as visuospatial material were assessed. Findings suggest that particularly reduced efficiency in visuospatial short-term memory is associated with Tower task planning deficits in children with HFA.

Event-based prospective memory performance in autism spectrum disorder

The purpose of the present study was to investigate event-based prospective memory performance in individuals with autism spectrum disorder and to explore possible relations between laboratory-based prospective memory performance and everyday performance. Nineteen children and adolescents with autism spectrum disorder and 19 matched neurotypical controls participated. The laboratory-based prospective memory test was embedded in a visuo-spatial working memory test and required participants to remember to respond to a cue-event. Everyday planning performance was assessed with proxy ratings. Although parents of the autism group rated their children's everyday performance as significantly poorer than controls' parents, no group differences were found in event-based prospective memory. Nevertheless, individual differences in laboratory-based and everyday performances were related. Clinical implications of these findings are discussed.