Evidence for executive dysfunction in autism

Profiles of executive function in parents and siblings of individuals with autism spectrum disorders

Delineation of a cognitive endophenotype for autism is useful both for exploring the genetic mechanisms underlying the disorder and for identifying which cognitive traits may be primary to it. This study investigated whether first-degree relatives of individuals with autism spectrum disorders (ASDs) demonstrate a specific profile of performance on a range of components of executive function (EF), to determine whether EF deficits represent possible endophenotypes for autism. Parents and siblings of ASD and control probands were tested on EF tasks measuring planning, set-shifting, inhibition and generativity. ASD parents showed poorer performance than control parents on a test of ideational fluency or generativity, and ASD fathers demonstrated a weakness in set-shifting to a previously irrelevant dimension. ASD siblings revealed a mild reduction in ideational fluency and a weakness in non-verbal generativity when compared with control siblings. Neither ASD parents nor siblings displayed significant difficulties with planning or inhibition. These results indicated that the broad autism phenotype may not be characterized primarily by impairments in planning and cognitive flexibility, as had been previously proposed. Weaknesses in generativity emerged as stronger potential endophenotypes in this study, suggesting that this aspect of EF should play a central role in cognitive theories of autism. However, discrepancies in the EF profile demonstrated by parents and siblings suggest that factors related to age or parental responsibility may affect the precise pattern of deficits observed.

Slowing down presentation of facial movements and vocal sounds enhances facial expression recognition and induces facial-vocal imitation in children with autism

This study examined the effects of slowing down presentation of facial expressions and their corresponding vocal sounds on facial expression recognition and facial and/or vocal imitation in children with autism. Twelve autistic children and twenty-four normal control children were presented with emotional and non-emotional facial expressions on CD-Rom, under audio or silent conditions, and under dynamic visual conditions (slowly, very slowly, at normal speed) plus a static control. Overall, children with autism showed lower performance in expression recognition and more induced facial-vocal imitation than controls. In the autistic group, facial expression recognition and induced facial-vocal imitation were significantly enhanced in slow conditions. Findings may give new perspectives for understanding and intervention for verbal and emotional perceptive and communicative impairments in autistic populations.

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

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

Motor persistence and inhibition in autism and ADHD

The present study compared performance of children with Attention-Deficit/Hyperactivity Disorder (ADHD) and high functioning autism (HFA) with that of controls on 4 tasks assessing 2 components of motor control: motor response inhibition and motor persistence. A total of 136 children (52 ADHD, 24 HFA, 60 controls) ages 7 to 13 years completed 2 measures of motor inhibition (Conflicting Motor Response and Contralateral Motor Response Tasks) and 2 measures of motor persistence (Lateral Gaze Fixation and NEPSY Statue). After controlling for age, IQ, gender, and basic motor speed, children with ADHD performed significantly more poorly than controls on the Conflicting Motor Response and Contralateral Motor Response Tasks, as well as on Statue. In contrast, children with HFA achieved lower scores than controls only on measures of motor persistence, with no concomitant impairment on either motor inhibition task. These results are consistent with prior research that has demonstrated relatively spared motor inhibition in autism. The findings highlight the utility of brief assessments of motor control in delineating the unique neurobehavioral phenotypes of ADHD and HFA.

Response Times of Children and Adolescents with Asperger Syndrome on an ‘Advanced’ Test of Theory of Mind

In the present study the response times of 10- to 20-year-old participants with Asperger syndrome (AS) (N=21) of normal intelligence and a control group of typically developing individuals (N=20) were recorded on a new 'advanced' test of theory of mind. This test taps the ability to make mental-state inferences versus physical-state inferences in a story context. The participants with AS were significantly slower than the controls on both tasks. In addition, the differences in response times between mental- and physical-state inference were significantly larger in the AS group than in the control group, suggesting that the clinical group experienced more problems than the controls in making inferences about mental states than about physical states.

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.

The hyper-systemizing, assortative mating theory of autism

The hyper-systemizing theory of autism proposes that the systemizing mechanism is set too high in people with autism. As a result, they can only cope with highly lawful systems, and cannot cope with systems of high variance or change (such as the social world of other minds). They appear 'change-resistant'. This proposal extends the extreme male brain theory of autism. Finally, evidence is reviewed for autism being the genetic result of assortative mating of two high systemizers.

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.

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.

High functioning children with autism spectrum disorder: A novel test of multitasking

High functioning children with a diagnosis of autism or Asperger's syndrome (HF-ASD) often experience difficulties organising goal-directed actions in their day-to-day lives, requiring support to schedule daily activities. This study aimed to capture these everyday difficulties experimentally using multitasking, a methodology that taps into the cognitive processes necessary for successful goal-directed activities in everyday life. We investigated multitasking in children with HF-ASD using a novel multitask test, the Battersea Multitask Paradigm. Thirty boys participated in the study, 14 with HF-ASD and 16 typically developing controls, matched for age and IQ. Group differences in multitasking were observed. Participants with HF-ASD were less efficient at planning, attempted fewer tasks, switched inflexibly between tasks and broke performance rules more frequently than controls.

Executive function deficits in autism spectrum disorders and attention-deficit/hyperactivity disorder: Examining profiles across domains and ages

Deficits in 'executive function' (EF) are characteristic of several clinical disorders, most notably Autism Spectrum Disorders (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD). In this study, age- and IQ-matched groups with ASD, ADHD, or typical development (TD) were compared on a battery of EF tasks tapping three core domains: response selection/inhibition, flexibility, and planning/working memory. Relations between EF, age and everyday difficulties (rated by parents and teachers) were also examined. Both clinical groups showed significant EF impairments compared with TD peers. The ADHD group showed greater inhibitory problems on a Go-no-Go task, while the ASD group was significantly worse on response selection/monitoring in a cognitive estimates task. Age-related improvements were clearer in ASD and TD than in ADHD. At older (but not younger) ages, the ASD group outperformed the ADHD group, performing as well as the TD group on many EF measures. EF scores were related to specific aspects of communicative and social adaptation, and negatively correlated with hyperactivity in ASD and TD. Within the present groups, the overall findings suggested less severe and persistent EF deficits in ASD (including Asperger Syndrome) than in ADHD.

Pseudo-random number generation in children with high-functioning autism and Asperger's disorder: further evidence for a dissociation in executive functioning?

The repetitive, stereotyped and obsessive behaviours, which are core diagnostic features of autism, are thought to be underpinned by executive dysfunction. This study examined executive impairment in individuals with autism and Asperger's disorder using a verbal equivalent of an established pseudo-random number generating task. Different patterns of disinhibition emerged in the autism (n = 12) and Asperger's disorder (n = 12) groups. Consistent with previous research, the autism group repeated single numbers (e.g. 2, 2, 2) more frequently than the control group. In contrast to past research suggesting intact executive abilities, this study found that the Asperger's disorder group generated more repetitive number patterns (e.g. 45, 45) than the controls. Executive functioning in children with Asperger's disorder may be particularly vulnerable to a lack of visual cueing and concrete rules. Qualitative differences in executive dysfunction between these groups may implicate differential disruption within the fronto-striatal circuitry.

Autism at the beginning: microstructural and growth abnormalities underlying the cognitive and behavioral phenotype of autism

Autistic symptoms begin in the first years of life, and recent magnetic resonance imaging studies have discovered brain growth abnormalities that precede and overlap with the onset of these symptoms. Recent postmortem studies of the autistic brain provide evidence of cellular abnormalities and processes that may underlie the recently discovered early brain overgrowth and arrest of growth that marks the first years of life in autism. Alternative origins and time tables for these cellular defects and processes are discussed. These cellular and growth abnormalities are most pronounced in frontal, cerebellar, and temporal structures that normally mediate the development of those same higher order social, emotional, speech, language, speech, attention, and cognitive functions that characterize autism. Cellular and growth pathologies are milder and perhaps nonexistent in other structures (e.g., occipital cortex), which are known to mediate functions that are often either mildly affected or entirely unaffected in autistic patients. It is argued that in autism, higher order functions largely fail to develop normally in the first place because frontal, cerebellar, and temporal cellular and growth pathologies occur prior to and during the critical period when these higher order neural systems first begin to form their circuitry. It is hypothesized that microstructural maldevelopment results in local and short distance overconnectivity in frontal cortex that is largely ineffective and in a failure of long-distance cortical-cortical coupling, and thus a reduction in frontal-posterior reciprocal connectivity. This altered circuitry impairs the essential role of frontal cortex in integrating information from diverse functional systems (emotional, sensory, autonomic, memory, etc.) and providing context-based and goal-directed feedback to lower level systems.

Verbal and spatial working memory in autism

Verbal and spatial working memory were examined in high-functioning children, adolescents, and adults with autism compared to age and cognitive-matched controls. No deficit was found in verbal working memory in the individuals with autism using an N-back letter task and standardized measures. The distinction between the N-back task and others used previously to infer a working memory deficit in autism is that this task does not involve a complex cognitive demand. Deficits were found in spatial working memory. Understanding the basis for the dissociation between intact verbal working memory and impaired spatial working memory and the breakdown that occurs in verbal working memory as information processing demands are increased will likely provide valuable insights into the neural basis of autism.

Spatial cognition in autism spectrum disorders: superior, impaired, or just intact?

The profile of spatial ability is of interest across autism spectrum disorders (ASD) because of reported spatial strengths in ASD and due to the recent association of Asperger's syndrome with Nonverbal Learning Disability. Spatial functions were examined in relation to two cognitive theories in autism: the central coherence and executive function (EF) theories. Performance on spatial tasks, EFs, and global/local processing was compared in children with ASD and controls. While the ASD group had faster reaction times on the Embedded Figures task, spatial performance was intact, but not superior, on other tasks. There was no evidence for impairments in EF or in processing global/local information, therefore contradicting these two theories. The implications of these results for these two theories are discussed.

Goal-Directed Action Representation in Autism

The aim of the present study was to investigate the ability of individuals with autism to represent goal-directed behavioural actions. We compared the performance of subjects with autism (n=16), mentally retarded subjects (n=14) and normal healthy subjects (n=15) in a sequencing task consisted in arranging pictures of single events in their appropriate order so as to make coherent stories. Three types of actions were presented: (a) actions on objects; (b) actions on objects in a broader spatio-temporal context; (c) interactive actions. Autistic subjects were impaired in arranging sequences of actions on objects, as compared to both control groups. This impairment might contribute to explaining both executive deficits and difficulties in understanding others' behaviour in autism.

Language, social, and executive functions in high functioning autism: a continuum of performance

This study examined language and executive functions (EF) in high-functioning school-aged individuals with autism and individually matched controls. Relationships between executive, language, and social functioning were also examined. Participants with autism exhibited difficulty on measures of expressive grammar, figurative language, planning, and spatial working memory. A mixed profile of impaired and enhanced abilities was noted in set-shifting. While controls showed the typical increase in errors when shifting sets from an intra-dimensional to an extra-dimensional stimulus, this pattern was not noted in participants with autism. Relationships between EF, language, and social performance were weak to non-existent. Implications for theories of core deficit in autism and dissociable nature of the language and executive impairments in autism are discussed.

Functions of frontostriatal systems in cognition: comparative neuropsychopharmacological studies in rats, monkeys and humans

A comparative and integrated account is provided of the evidence that implicates frontostriatal systems in neurodegenerative and neuropsychiatric disorders. Specifically, we have made detailed comparisons of performance following basal ganglia disease such as Parkinson's disease, with other informative groups, including Alzheimer's disease, schizophrenia and attention deficit/hyperactivity disorder and structural damage to the frontal lobes themselves. We have reviewed several behavioural paradigms including spatial attention and set-shifting, working memory and decision-making tasks in which optimal performance requires the operation of several cognitive processes that can be successfully dissociated with suitable precision in experimental animals. The role of ascending neurotransmitter systems are analysed from the perspective of different interactions with the prefrontal cortex. In particular, the role of dopamine in attentional control and spatial working memory is surveyed with reference to its deleterious as well as facilitatory effects. Parallels are identified in humans receiving dopaminergic medication, and with monkeys and rats with frontal dopamine manipulations. The effects of serotonergic manipulations are also contrasted with frontal lobe deficits observed in both humans and animals. The main findings are that certain tests of frontal lobe function are very sensitive to several neurocognitive and neuropsychiatric disorders. However, the nature of some of these deficits often differs qualitatively from those produced by frontal lobe lesions, and animal models have been useful in defining various candidate neural systems thus enabling us to translate basic laboratory science to the clinic, as well as in the reverse direction.

Disorganization: the forgotten executive dysfunction in high-functioning autism (HFA) spectrum disorders

Executive function (EF) abilities were investigated in 72 children with high-functioning autism (HFA) spectrum disorders through the collection of parent ratings and performance on laboratory measures of EF. In addition, discrepancy analysis was used to isolate executive functioning on tasks that carry multiple demands. Comparison of HFA and Asperger Disorder (AD) groups did not reveal consistent differences in EF. Results did indicate global EF deficits in the combined group of children with HFA and AD. Within the EF domain, specific deficits in flexibility and organization were most prominent.

Neural correlates of executive function in autistic spectrum disorders

BACKGROUND

Some clinical characteristics of high-functioning individuals with autistic spectrum disorder (ASD) such as repetitive stereotyped behaviors, perseveration, and obsessionality have been related to executive function (EF) deficits, more specifically to deficits in inhibitory control and set shifting and mediating frontostriatal neural pathways. However, to date, no functional imaging study on ASD has investigated inhibition and cognitive flexibility and no one has related EF brain activation to brain structure.

METHODS

We compared brain activation (using functional magnetic resonance imaging) in 10 normal intelligence adults with ASD and 12 healthy control subjects during three different EF tasks: 1) motor-inhibition (GO/NO-GO); 2) cognitive interference-inhibition (spatial STROOP); and 3) set shifting (SWITCH). Using voxel-based morphometry, we investigated if cortical areas which were functionally different in people with ASD were also anatomically abnormal.

RESULTS

Compared with control subjects, ASD individuals showed significantly increased brain activation in 1) left inferior and orbital frontal gyrus (motor-inhibition); 2) left insula (interference-inhibition); and 3) parietal lobes (set shifting). Moreover, in individuals with ASD, increased frontal gray matter density and increased functional activation shared the same anatomical location.

CONCLUSIONS

Our findings suggest an association between successful completion of EF tasks and increased brain activation in people with ASD, which partially may be explained by differences in brain anatomy.

Is There A Common Neuronal Basis for Autism and Catatonia?

Neuronal bases for autism and catatonia are unknown although integrative theories may soon become feasible as research in autism and catatonia advances. Catatonia and autism may both qualify as neurobiological syndromes in their own right. There is emerging evidence that catatonia may be a common syndrome in autism. Although the relation between autism and catatonia is unclear, coexpression of autism and catatonia may be due to abnormalities in common neuronal circuitries. This possibility constitutes another level of complexity to neurobiological inquiry, but also provides an opportunity to advance our understanding of both disorders. There is a great potential benefit in studying the relation between catatonia and autism in order to focus future research on subtype-specific causes and treatments. Future research avenues are outlined.

Examining the relationship between executive functions and restricted, repetitive symptoms of Autistic Disorder

The executive function theory was utilized to examine the relationship between cognitive process and the restricted, repetitive symptoms of Autistic Disorder (AD). Seventeen adults with AD were compared to 17 nonautistic controls on a new executive function battery (Delis-Kaplin Executive Function Scales). Restricted, repetitive symptoms were measured by a variety of instruments (i.e., the Autism Diagnostic Observation Schedule, Autism Diagnostic Interview-Revised, Gilliam Autism Rating Scale, and the Aberrant Behavior Checklist). The study replicated the executive function profile that has been reported in adults with AD. In addition to the replication findings, the study found several executive processes (i.e., cognitive flexibility, working memory, and response inhibition) were highly related to the restrictive, repetitive symptoms of AD; whereas, other executive process (i.e., planning and fluency) were not found to be significantly correlated with restricted, repetitive symptoms. Similarly, we found an executive function model consisting of relative strengths and deficits was the best predictor of restricted, repetitive symptoms of autism. The implications for the executive function theory and how the theory predicts core symptoms of autism are discussed.

Subtle executive impairment in children with autism and children with ADHD

BACKGROUND

The executive functions of inhibition, planning, flexible shifting of actions, and working memory are commonly reported to be impaired in neurodevelopmental disorders.

METHOD

We compared these abilities in children (8-12 years) with high functioning autism (HFA, n = 17), attention deficit-hyperactivity disorder (ADHD, n = 21) and healthy controls (n = 32). Response inhibition was assessed using the Stroop Color and Word Test (Golden, 1978). Problem solving, set-shifting, and nonverbal memory were assessed using three tasks, respectively, from the CANTAB (Cambridge Cognition, 1996): the Stockings of Cambridge task; the Intra-Dimensional/Extra-Dimensional set-shifting task; and the Spatial Working Memory task (SWM) with tokens hidden behind 3, 4, 6, and 8 boxes.

RESULTS

There were no group differences on the response inhibition, planning, or set-shifting tasks. On the SWM task, children with HFA made significantly more between-search errors compared with controls on both the most difficult problems (8-box) and on the mid-difficulty problems (6-box); however, children with ADHD made significantly more errors compared to controls on the most difficult (8-box) problems only.

CONCLUSION

Our findings suggest that spatial working memory is impaired in both ADHD and HFA, and more severely in the latter. More detailed investigation is needed to examine the mechanisms that differentially impair spatial working memory, but on this set of tasks there appears to be sparing of other executive functions in these neuropsychiatric developmental disorders.

Assessment of hot and cool executive function in young children: age-related changes and individual differences

Although executive function (EF) is often considered a domain-general cognitive function, a distinction has been made between the "cool" cognitive aspects of EF more associated with dorsolateral regions of prefrontal cortex and the "hot" affective aspects more associated with ventral and medial regions (Zelazo and Mller, 2002). Assessments of EF in children have focused almost exclusively on cool EF. In this study, EF was assessed in 3- to 5-year-old children using 2 putative measures of cool EF (Self-Ordered Pointing and Dimensional Change Card Sort) and 2 putative measures of hot EF (Children's Gambling Task and Delay of Gratification). Findings confirmed that performance on both types of task develops during the preschool period. However, the measures of hot and cool EF showed different patterns of relations with each other and with measures of general intellectual function and temperament. These differences provide preliminary evidence that hot and cool EF are indeed distinct, and they encourage further research on the development of hot EF.

Three types of source monitoring by children with and without autism: the role of executive function

Earlier investigations have found mixed evidence of source monitoring impairment in autism. The present study examined three types of source monitoring ability in children with autism and typically developing children. In three different conditions, participants were presented with word lists after which they were required to recall the source of the word for reality, external and internal source monitoring tasks. Group differences were found across all three conditions, with the comparison group outperforming the children with autism. The pattern of performance across the three conditions, however, was comparable for the two groups. Specifically, performance was higher on the reality monitoring task than either the external or internal source tasks. We suggest that the overall impairment found for the children with autism may be due to broader impairments in executive function.

Humor in autism and Asperger syndrome

Research has shown that individuals with autism and Asperger syndrome are impaired in humor appreciation, although anecdotal and parental reports provide some evidence to the contrary. This paper reviews the cognitive and affective processes involved in humor and recent neurological findings. It examines humor expression and understanding in autism and Asperger syndrome in the context of the main psychological theories (Theory of Mind, Executive Functions, Weak Central Coherence and Laterization models) and associated neural substrates. In the concluding sections, examples of humor displayed by individuals with autism/Asperger syndrome which appear to challenge the above theories are analyzed and areas for further research are suggested.

Source memory in adolescents and adults with Asperger's syndrome

Memory difficulties in autism are observed mainly on measures like free recall, where test procedures provide no support for memory. When support is present, such as in cued recall, difficulties are less evident. Such observations may explain the mixed findings on source memory in autism. Bennetto, Pennington and Rogers (Child Development, 67, 1816-1835) found increased earlier-list intrusions in a multi-list free-recall paradigm (support absent), yet Farrant, Blades and Boucher (Journal of Autism and Developmental Disorders, 28, 43-50) reported no impairment in identification of who had spoken a particular word at study (support present). We tested the effects on source memory of presence or absence of support for source in participants with Asperger's syndrome. The Asperger participants' overall deficit in source memory was largely eliminated when source was supported at test.

The role of the medial temporal lobe in autistic spectrum disorders

The neural basis of autistic spectrum disorders (ASDs) is poorly understood. Studies of mnemonic function in ASD suggest a profile of impaired episodic memory with relative preservation of semantic memory (at least in high-functioning individuals). Such a pattern is consistent with developmental hippocampal abnormality. However, imaging evidence for abnormality of the hippocampal formation in ASD is inconsistent. These inconsistencies led us to examine the memory profile of children with ASD and the relationship to structural abnormalities. A cohort of high-functioning individuals with ASD and matched controls completed a comprehensive neuropsychological memory battery and underwent magnetic resonance imaging for the purpose of voxel-based morphometric analyses. Correlations between cognitive/behavioural test scores and quantified results of brain scans were also carried out to further examine the role of the medial temporal lobe in ASD. A selective deficit in episodic memory with relative preservation of semantic memory was found. Voxel-based morphometry revealed bilateral abnormalities in several areas implicated in ASD including the hippocampal formation. A significant correlation was found between parental ratings reflecting autistic symptomatology and the measure of grey matter density in the junction area involving the amygdala, hippocampus and entorhinal cortex. The data reveal a pattern of impaired and relatively preserved mnemonic function that is consistent with a hippocampal abnormality of developmental origin. The structural imaging data highlight abnormalities in several brain regions previously implicated in ASD, including the medial temporal lobes.

Central coherence in typically developing preschoolers: does it cohere and does it relate to mindreading and executive control?

BACKGROUND

Frith and Happé (1994) describe central coherence (CC) as the normal tendency to integrate individual elements into a coherent whole, a cognitive style which varies in the general population. Individuals with autism are at the extreme (weak) end of the continuum of coherence. There has been debate over whether CC is independent from other psychological functions such as theory of mind and executive control.

METHODS

We examined the validity of the CC construct in 76 typically developing 4- and 5-year-old children using four visuospatial coherence tasks. We also investigated the extent to which individual differences in performance on CC measures were associated with individual differences on measures of mindreading and executive functioning (EF).

RESULTS

Unexpectedly, the CC variables were not highly intercorrelated and did not form a single coherence factor. Instead, the results revealed a two-factor structure, one of which corresponded to visuospatial constructional ability. Correlations between the emerging factors of coherence and mindreading ability were weak, even when developmental differences in age and verbal and nonverbal ability were taken into account. In contrast, visuospatial constructional ability was reliably related to measures of EF, whilst correlations between EF and the second CC factor were very weak.

CONCLUSIONS

CC in typically developing preschoolers is not a unitary construct. Whilst there is little relationship between CC and mindreading abilities in these young children, executive control appears to be associated with one aspect of coherence: visuospatial construction.

Neuroepileptic correlates of autistic symptomatology in tuberous sclerosis

Tuberous sclerosis is a genetic condition that is strongly associated with the development of an autism spectrum disorder. However, there is marked variability in expression, and only a subset of children with tuberous sclerosis develop autism spectrum disorder. Clarification of the mechanisms that underlie the association and variability in expression will potentially throw light on the biological processes involved in the etiology of idiopathic forms of autism spectrum disorder. Current evidence indicates that the likelihood of a child with tuberous sclerosis developing an autism spectrum disorder is greater if the child has a mutation in the TSC2 gene, although autism can and does develop in children with TSC1 mutations. The likelihood is also greater if the child has early-onset infantile spasms that are difficult to control, especially if there is an epileptiform focus in the temporal lobes. The emerging evidence is consistent with the notion that early onset electrophysiological disturbances within the temporal lobes (and perhaps other locations) has a deleterious effect on the development and establishment of key social cognitive representations concerned with processing social information, perhaps especially from faces. However, alternative mechanisms to account for the findings cannot yet be ruled out. Future research will have to employ prospective longitudinal designs and treatment trials to clarify the processes involved.

Localized enlargement of the frontal cortex in early autism

BACKGROUND

Evidence from behavioral, imaging, and postmortem studies indicates that the frontal lobe, as well as other brain regions such as the cerebellum and limbic system, develops abnormally in children with autism. It is not yet clear to what extent the frontal lobe is affected; that is, whether all regions of frontal cortex show the same signs of structural maldevelopment.

METHODS

In the present study, we measured cortical volume in four subregions of the frontal cortex in 2-year-old to 9-year-old boys with autism and normal control boys.

RESULTS

The dorsolateral region showed a reduced age effect in patients when compared with control subjects, with a predicted 10% increase in volume from 2 years of age to 9 years of age compared with a predicted 48% increase for control subjects. In a separate analysis, dorsolateral and medial frontal regions were significantly enlarged in patients aged 2 to 5 years compared with control subjects of the same age, but the precentral gyrus and orbital cortex were not.

CONCLUSIONS

These data indicate regional variation in the degree of frontocortical overgrowth with a possible bias toward later developing or association areas. Possible mechanisms for these regional differences are discussed.

Early amygdala damage disrupts performance on medial prefrontal cortex-related tasks but spares spatial learning and memory in the rat

Recent studies have demonstrated that the postnatal development of connections between the basolateral amygdala (BLA) and the medial prefrontal cortex (mPFC) mature around postnatal days 13-15 (pd13-15), whereas these between the BLA and other structures such as the nucleus accumbens and the mediodorsal thalamus are completed by pd7. Accordingly, it is hypothesized that mPFC cytoarchitecture and hence its function may be specifically affected by neonatal (i.e. on pd7) but not later induced (i.e. on pd21) damage to the BLA. To test this hypothesis, rats received excitotoxic lesions to the BLA on either pd7 or pd21 and were subjected to two tests putatively sensitive to mPFC dysfunction, namely food hoarding and spontaneous alternation. In addition, rats were tested for spatial learning and memory, to determine any possible effects on hippocampal function. Consistent with the documented effects of mPFC lesions, pd7 damage to the BLA impaired spontaneous alternation and food hoarding performance, an effect that was not found in rats with BLA lesions induced on pd21. Spatial learning and memory, however, were not affected by the (neonatal) lesion procedure. Together, these results indicate that neonatal BLA damage affects species-specific sequential behavior and flexibility, which may be attributed to abnormal functioning of the mPFC.

Executive dysfunction and its relation to language ability in verbal school-age children with autism

This study examined executive dysfunction and its relation to language ability in verbal school-age children with autism. Participants were 37 children with autism and 31 nonautistic comparison participants who were matched on age and on verbal and nonverbal IQ but not on language ability, which was lower in the autism group. Children with autism exhibited deficits compared to the comparison group across all 3 domains of executive function that were assessed including working memory (Block Span Backward; Isaacs & Vargha-Khadem, 1989), working memory and inhibitory control (NEPSY Knock-Tap; Korkman, Kirk, & Kemp, 1998), and planning (NEPSY Tower; Korkman et al., 1998). Children with autism were less developed than the comparison group in their language skills, but correlational analyses revealed no specific association between language ability and executive performance in the autism group. In contrast, executive performance was positively correlated with language ability in the comparison group. This pattern of findings suggest that executive dysfunction in autism is not directly related to language impairment per se but rather involves an executive failure to use of language for self-regulation.

Performance on Cambridge Neuropsychological Test Automated Battery subtests sensitive to frontal lobe function in people with autistic disorder: evidence from the Collaborative Programs of Excellence in Autism network

Recent structural and functional imaging work, as well as neuropathology and neuropsychology studies, provide strong empirical support for the involvement of frontal cortex in autism. The Cambridge Neuropsychological Test Automated Battery (CANTAB) is a computer-administered set of neuropsychological tests developed to examine specific components of cognition. Previous studies document the role of frontal cortex in performance of two CANTAB subtests: the Stockings of Cambridge, a planning task, and the Intradimensional/Extradimensional Shift task, a measure of cognitive set shifting. To examine the integrity of frontal functions, these subtests were administered to 79 participants with autism and 70 typical controls recruited from seven universities who are part of the Collaborative Programs of Excellence in Autism network. The two groups were matched on age, sex, and full-scale IQ. Significant group differences were found in performance on both subtests, with the autism group showing deficits in planning efficiency and extradimensional shifting relative to controls. Deficits were found in both lower- and higher-IQ individuals with autism across the age range of 6 to 47 years. Impairment on the CANTAB executive function subtests did not predict autism severity or specific autism symptoms (as measured by the ADI-R and ADOS), but it was correlated with adaptive behavior. If these CANTAB subtests do indeed measure prefrontal function, as suggested by previous research with animals and lesion patients, this adds to the accumulating evidence of frontal involvement in autism and indicates that this brain region should remain an active area of investigation.

The use and understanding of virtual environments by adolescents with autistic spectrum disorders

The potential of virtual environments for teaching people with autism has been positively promoted in recent years. The present study aimed to systematically investigate this potential with 12 participants with autistic spectrum disorders (ASDs), each individually matched with comparison participants according to either verbal IQ or performance IQ, as well as gender and chronological age. Participants practised using a desktop 'training' virtual environment, before completing a number of tasks in a virtual café. We examined time spent completing tasks, errors made, basic understanding of the representational quality of virtual environments and the social appropriateness of performance. The use of the environments by the participants with ASDs was on a par with their PIQ-matched counterparts, and the majority of the group seemed to have a basic understanding of the virtual environment as a representation of reality. However, some participants in the ASD group were significantly more likely to be judged as bumping into, or walking between, other people in the virtual scene, compared to their paired matches. This tendency could not be explained by executive dysfunction or a general motor difficulty. This might be a sign that understanding personal space is impaired in autism. Virtual environments might offer a useful tool for social skills training, and this would be a valuable topic for future research.

Application of a neuropsychological activation probe with SPECT: the 'Tower of London' task in healthy volunteers

BACKGROUND

Human planning is a complex mental process that may be evaluated by the 'Tower of London' (TOL) task, which includes setting up and maintaining multiple subgoals at the same time. Although positron emission tomography and functional magnetic resonance imaging have provided reliable data on the recruitment of a neural network engaged in planning tasks, the experimental settings of these studies cannot be applied in clinical conditions. Hence, this study reports on the TOL task under classical neuropsychological test conditions using single photon emission computed tomography (SPECT) activation in 10 healthy subjects.

METHODS

Participants first performed a control task and then an activation task, i.e., the TOL planning task In the planning task, subjects were required to change, in the minimum number of moves possible, an initial arrangement of beads to match a goal arrangement. Subjects solved a set of eight TOL problems of increasing difficulty. A control task was designed such that it eliminates planning abilities, which is the process of interest. Planning times and accuracy were measured as performance parameters and functional imaging data were analysed with statistical parametric mapping (SPM99) to determine significant voxel-wise activations between the planning task and the control task.

RESULTS

Both overall and for each difficulty level, measures of accuracy were within the normal range. Similar results were found for the overall thinking time and thinking times of each difficulty level. That is, performance of the healthy subjects during the TOL task replicated the typical pattern of results found with appropriate control samples in the literature. Also, activation of the right prefrontal cortex was consistent with other functional imaging results, thereby validating the use of the TOL task in a SPECT activation paradigm.

CONCLUSIONS

Based on the present study it may be concluded that the close resemblance of the test conditions of the SPECT activation procedure with those of the TOL task in the investigation room constitutes a major advantage for future application of the SPECT activation procedure in clinical conditions.

Abnormal activity patterns in premotor cortex during sequence learning in autistic patients

BACKGROUND

Evidence for frontal abnormality in autism has accumulated in recent years. Our own studies have shown abnormal activation in prefrontal cortex during finger tapping and visuomotor coordination. Studies in healthy adults suggest reduced premotor and increased prefrontal activity during advanced learning stages. We examined hemodynamic changes during visuomotor learning in autistic patients.

METHODS

We studied eight high-functioning autistic patients and eight control subjects during learning of an 8-digit sequence over a period of 8 min, using functional magnetic resonance imaging.

RESULTS

Autistic patients showed overall less prefrontal activation during late visuomotor learning; however, the main finding was a complementary one of enhanced activation in right pericentral and premotor cortex. In the autism group, Brodmann areas 3, 4, and 6 of the right hemisphere became more involved during late learning stages (trials 25-48), compared with early stages (trials 1-24). This effect was not seen in the control group.

CONCLUSIONS

Our findings suggests that in autistic patients 1) primary sensorimotor and premotor cortex, which is normally predominant in early stages of visuomotor learning, plays an atypical role in later stages, even when learning is evident; and 2) handedness and side of execution interact with asymmetry of visuomotor learning activations, contrary to what is seen in normal adults.

The relationship of theory of mind and executive functions to symptom type and severity in children with autism

Although neurocognitive impairments in theory of mind and in executive functions have both been hypothesized to play a causal role in autism, there has been little research investigating the explanatory power of these impairments with regard to autistic symptomatology. The present study examined the degree to which individual differences in theory of mind and executive functions could explain variations in the severity of autism symptoms. Participants included 31 verbal, school-aged children with autism who were administered a battery of tests assessing the understanding of mental states (knowledge and false belief) and executive control skills (working memory, combined working memory and inhibitory control, and planning) and who were behaviorally evaluated for autism severity in the three core symptom domains. Whereas theory of mind and executive control abilities explained the significant variance beyond that accounted for by language level in communication symptoms, neither explained the significant variance in reciprocal social interaction or repetitive behaviors symptoms. These findings are discussed in terms of a proposed distinction between higher level, cognitive-linguistic aspects of theory of mind and related executive control skills, and more fundamental social-perceptual processes involved in the apprehension of mental state information conveyed through eyes, faces, and voices, which may be more closely linked to autistic deficits in social reciprocity.

Theories of conduct disorder: a causal modelling analysis

BACKGROUND

If a clinician has to make decisions on diagnosis and treatment, he or she is confronted with a variety of causal theories. In order to compare these theories a neutral terminology and notational system is needed. The Causal Modelling framework involving three levels of description - biological, cognitive and behavioural - has previously been used to compare causal accounts for dyslexia and autism.

METHOD

In this article we present this framework and explore its application to four causal theories of conduct disorder. We discuss the problems we encountered in this application and evaluate both the framework and the theories of conduct disorder.

CONCLUSIONS

It was possible to capture parts of the theories of conduct disorder in the Causal Modelling framework but a multi-model approach may be necessary for the alternative theories of conduct disorder we evaluate. The application of the framework helps to see the relationships among the various theories of aspects of conduct disorder and demonstrates the need for more explicitness in the causal theories.

How specific are executive functioning deficits in attention deficit hyperactivity disorder and autism?

BACKGROUND

The objective of this study is to identify intact and deficient cognitive processes in children with attention deficit hyperactivity disorder (ADHD) and children with high functioning autism (HFA).

METHOD

Three rigorously diagnosed groups of children aged between 6 and 12 years (54 ADHD, 41 HFA, and 41 normal controls) were tested on a wide range of tasks related to five major domains of executive functioning (EF): inhibition, visual working memory, planning, cognitive flexibility, and verbal fluency. In addition, the role of comorbid oppositional defiant disorder (ODD) and comorbid conduct disorder (CD) in ADHD was investigated by directly comparing 20 children with ADHD and 34 children with comorbid ADHD + ODD/CD.

RESULTS

ADHD was associated with EF deficits in inhibiting a prepotent response and verbal fluency. Children with HFA demonstrated deficits in all EF domains, except interference control and working memory. The HFA group showed more difficulties than the ADHD group with planning and cognitive flexibility. The comorbid ADHD + ODD/CD group did not show a distinctive pattern of performance on the EF tests compared to the ADHD group.

CONCLUSION

The present study indicates that children with HFA exhibit more generalised and profound problems with EF tasks compared to children with ADHD.

Initial and concurrent planning in solutions to well-structured problems

Two experiments are reported, which consider planning behaviour in the context of a well-structured problem. One question in the problem-solving literature is to what extent planning a solution to a problem takes place before attempting that problem and whether this takes precedence over planning while solving a problem, hereafter referred to as concurrent planning. An additional question is whether the adoption of one mode of planning confers a performance advantage and under what circumstances one strategy is adopted in preference to others. The studies reported here set out to investigate the effects on performance of adopting different modes of planning and whether there is any relationship between the adoption of different strategic approaches and problem-solving performance. The results of these studies suggest that initial planning can enhance problem-solving performance, but only when problems remain relatively simple. As problem complexity increases the effects of initial planning appear to have little or no effect upon performance. In conclusion it is suggested that strategy use depends upon the interactions between individual preference for a given strategy, problem complexity, and the stage that one has reached in the development of a solution to a problem.

Practitioner review: computerized assessment of neuropsychological function in children: clinical and research applications of the Cambridge Neuropsychological Testing Automated Battery (CANTAB)

BACKGROUND

Computers have been used for a number of years in neuropsychological assessment to facilitate the scoring, interpretation, and administration of a variety of commonly used tests. There has been recent interest in applying computerized technology to pediatric neuropsychological assessment, which poses unique demands based on the need to interpret performance relative to the child's developmental level.

FINDINGS

However, pediatric neuropsychologists have tended to implement computers in the scoring, but not administration, of tests. This trend is changing based on the work of experimental neuropsychologists who frequently combine data obtained from test batteries with lesion or neuroimaging data allowing descriptions of brain-behavior relations to be made with increasing confidence. One such battery is the Cambridge Neuropsychological Testing Automated Battery (CANTAB), and current studies in which the CANTAB has been used to measure executive functions in children are reviewed.

CONCLUSIONS

Computerized batteries of this type can record aspects of performance that are difficult for psychometrists to achieve, and these may reflect activity in developing neural networks with more sensitivity than can be achieved with traditional tests. However, before computerized test administration becomes a routine part of pediatric neuropsychological assessment, several obstacles must be overcome. Despite these limitations, it is concluded that computerized assessment can improve the field by facilitating the collection of normative and clinical data.

Cognitive underpinnings of pretend play in autism

This article examines the cognitive underpinnings of spontaneous and prompted pretend play in 28 young children with autism, 24 children with other developmental disorders, and 26 typical children. The article compares theories that consider either theory of mind (ToM) or executive function (EF) to be causally important deficits in the development of pretend play in autism and important factors in pretend play. Each of these two theories posits a cognitive precursor to pretense, which would need to be present in typical development, and the absence of which could explain pretend play deficits in children with developmental disabilities such as autism. We tested which of these theories better predicts a child's production of pretend play. Children with autism were significantly delayed on pretend play scores. They also had significant deficits in our ToM measure, but not our EF measures. Regression analyses suggested a role for our measure of generativity, one of the EF measures.

Pitch memory, labelling and disembedding in autism

BACKGROUND

Autistic musical savants invariably possess absolute pitch ability and are able to disembed individual musical tones from chords. Enhanced pitch discrimination and memory has been found in non-savant individuals with autism who also show superior performance on visual disembedding tasks. These experiments investigate the extent that enhanced disembedding ability will be found within the musical domain in autism.

METHOD

High-functioning children with autism, together with age- and intelligence-matched controls, participated in three experiments testing pitch memory, labelling and chord disembedding.

RESULTS

The findings from experiment 1 showed enhanced pitch memory and labelling in the autism group. In experiment 2, when subjects were pre-exposed to labelled individual tones, superior chord segmentation was also found. However, in experiment 3, when disembedding performance was less reliant on pitch memory, no group differences emerged and the children with autism, like controls, perceived musical chords holistically.

CONCLUSION

These findings indicate that pitch memory and labelling is superior in autism and can facilitate performance on musical disembedding tasks. However, when task performance does not rely on long-term pitch memory, autistic children, like controls, succumb to the Gestalt qualities of chords.

Assessment of neuropsychological function through use of the Cambridge Neuropsychological Testing Automated Battery: performance in 4- to 12-year-old children

In this article, children's performance on subtasks from the Cambridge Neuropsychological Testing Automated Battery (CANTAB) is described. Two samples were recruited, one of which included children who spoke English as a second language. Children in this group also completed subtests from the Wechsler Intelligence Scale for Children-Third Revision (WISC-III). Despite the fact that ESL children scored over 1 SD below the norm on the WISC-III Vocabulary subtest, there were no CANTAB performance distinctions between primary versus secondary English-language speakers. In addition, several aspects of CANTAB performance were significantly correlated with verbal and nonverbal IQ. When developmental trends were examined, findings indicated that several aspects of frontal lobe function (memory span, working memory, and planning skills) are not functionally mature, by the age of 12 years. Implications for use of the CANTAB in clinical studies are discussed.

Spatial reversal as a measure of executive functioning in children with autism

The purpose of this experiment was to compare the executive functioning performance of children with autism with chronological- and verbal-matched controls in a spatial-reversal task. Three groups of children participated in this experiment. One group was identified as having autism (7 boys), the 2nd group contained 7 typically developing children (6 boys, 1 girl) who were matched to the 1st group based on their verbal performance, and the 3rd group contained 7 typically functioning children (6 boys, 1 girl) matched to the 1st group based on chronological age. Each group was given a spatial-reversal task containing 2 problems. In the 1st problem, children selected a toy on a particular side in a pair. In the 2nd problem, the contingencies were reversed such that children were to choose the toy on the opposite side. Children with autism generally performed worse than comparison groups as indicated by their overall higher rate of errors. However, these results must be qualified by considering the performance for each problem: Errors for the children with autism were infrequent during the 1st problem but increased in the 2nd, whereas errors for comparison children showed the opposite pattern. When these results from the spatial-reversal task were interpreted from the perspective of hypothesis-testing theory, the executive functioning deficiency of children with autism was found to involve the selection and testing of stereotypic response sets that were not likely to be revised or changed flexibly according to feedback from the environment or the demands of the task.

Understanding autism: insights from mind and brain

Autism is a developmental disorder characterized by impaired social interaction and communication as well as repetitive behaviours and restricted interests. The consequences of this disorder for everyday life adaptation are extremely variable. The general public is now more aware of the high prevalence of this lifelong disorder, with ca. 0.6% of the population being affected. However, the signs and symptoms of autism are still puzzling. Since a biological basis of autism was accepted, approaches from developmental cognitive neuroscience have been applied to further our understanding of the autism spectrum. The study of the behavioural and underlying cognitive deficits in autism has advanced ahead of the study of the underlying brain abnormalities and of the putative genetic mechanisms. However, advances in these fields are expected as methodological difficulties are overcome. In this paper, recent developments in the field of autism are outlined. In particular, we review the findings of the three main neuro-cognitive theories of autism: theory-of-mind deficit, weak central coherence and executive dysfunction.

Tower of London test performance in children with poor arithmetic skills

The Tower of London (TOL) has been used to assess executive functions in both children and adults with documented brain dysfunction. Like many other measures of executive function, it has not been widely used in the assessment of learning disabilities in children. However, if performance on the TOL discriminated among groups of children with different academic strengths and weaknesses, then it may be useful in identifying learning disability subtypes. The purpose of this study was to determine whether performance on the TOL would differ among 3 groups of children: those with arithmetic difficulties, those with reading difficulties, and those with no academic difficulties. The group with arithmetic difficulties exhibited significantly greater impairment on the TOL than either the group with reading difficulties or the group with no difficulties. The latter 2 groups performed similarly. The clinical utility of the TOL, as well as the relation between arithmetic deficits and executive functions, are discussed.