Verbal and spatial working memory in autism

Working memory, language skills, and autism symptomatology

While many studies have reported working memory (WM) impairments in autism spectrum disorders, others do not. Sample characteristics, WM domain, and task complexity likely contribute to these discrepancies. Although deficits in visuospatial WM have been more consistently documented, there is much controversy regarding verbal WM in autism. The goal of the current study was to explore visuospatial and verbal WM in a well-controlled sample of children with high-functioning autism (HFA) and typical development. Individuals ages 9–17 with HFA (n = 18) and typical development (n = 18), were carefully matched on gender, age, IQ, and language, and were administered a series of standardized visuospatial and verbal WM tasks. The HFA group displayed significant impairment across WM domains. No differences in performance were noted across WM tasks for either the HFA or typically developing groups. Over and above nonverbal cognition, WM abilities accounted for significant variance in language skills and symptom severity. The current study suggests broad WM limitations in HFA. We further suggest that deficits in verbal WM are observed in more complex tasks, as well as in simpler tasks, such as phonological WM. Increased task complexity and linguistic demands may influence WM abilities.

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.

Self-Rated Autistic-Like Traits and Capacity of Visual Working Memory

The effect on the capacity of visual working memory of spatial complexity (as defined by Garner's principle) in rotation and reflection transformation was examined in persons differing along the Autism Spectrum Quotient (AQ), using a change-detection task. On each trial, nine line segments were arrayed in simple, medium, and complex configurations, which were presented in memory and test displays. 27 participants (8 men, 19 women; M age = 22.3 yr., SD = 2.7) were asked whether the orientations of stimuli between two displays were the same or different. On the basis of their AQ scores out of 50 ( M AQ scores = 20.9, SD = 6.3), the participants were divided into groups with high ( n = 13; M AQ scores = 26.2, SD = 4.1) and low ( n = 12; M AQ scores = 15.3, SD = 2.7) self-reported autistic-like traits (High and Low AQ groups, 2 excluded for scores at the median). The results showed that spatial complexity affects the capacity of visual working memory for the Low AQ group but not for the High AQ group, suggesting the functional dissociation of spatial configuration and visual working memory in the High AQ group.

Noradrenergic moderation of working memory impairments in adults with autism spectrum disorder

In addition to having difficulties with social communications, individuals with an autism spectrum disorder (ASD) often also experience impairment in higher-order, executive skills. The present study examined the effects of pharmacological modulation of the norepinephrine system on the severity of such impairments. A sample of 14 high-functioning adults with ASD and a demographically-matched comparison group of 13 typically developing individuals participated. An AX continuous performance test (AX-CPT) was used to evaluate working memory and inhibitory control. AX-CPT performance was assessed following administration of a single dose of propranolol (a beta adrenergic antagonist) and following placebo (sugar pill) administration. Individuals with ASD performed more poorly than non-ASD individuals in the working memory condition (BX trials). Importantly, administration of propranolol attenuated this impairment, with the ASD group performing significantly better in the propranolol condition than the placebo condition. Working memory performance of the non-ASD group was unaffected by propranolol/placebo administration. No group or medication effects were observed for the inhibition condition (AY trials). The present findings suggest that norepinephrine may play a role in some, but not necessarily all, cognitive impairments associated with ASD. Additional research is needed to fully understand whether this role is primarily causal or compensatory in nature.

Thinking in Pictures as a cognitive account of autism

We analyze the hypothesis that some individuals on the autism spectrum may use visual mental representations and processes to perform certain tasks that typically developing individuals perform verbally. We present a framework for interpreting empirical evidence related to this "Thinking in Pictures" hypothesis and then provide comprehensive reviews of data from several different cognitive tasks, including the n-back task, serial recall, dual task studies, Raven's Progressive Matrices, semantic processing, false belief tasks, visual search, spatial recall, and visual recall. We also discuss the relationships between the Thinking in Pictures hypothesis and other cognitive theories of autism including Mindblindness, Executive Dysfunction, Weak Central Coherence, and Enhanced Perceptual Functioning.

Verbal problem-solving in autism spectrum disorders: a problem of plan construction?

Children with autism spectrum disorders (ASD) adopt less efficient strategies than typically developing controls (TD) on verbal problem-solving tests such as the Twenty Questions Task. This study examined the hypotheses that this can be explained by differences in (i) planning processes or (ii) selective attention. Twenty-two children with ASD and 21 TD controls matched for age (M(age) = 13:7) and cognitive ability (M(FSIQ) = 96.42) were tested on an adapted version of Twenty Questions and two planning tasks. ASD participants could recognize effective questions as well as TD participants on a forced-choice question discrimination task, but were observed to construct plans that were significantly less efficient. ASD performance was also specifically reduced when items could not be physically removed from the testing array, although this effect could be ameliorated by keeping a written record of participant questions during search. These findings indicate that ASD participants are sensitive to the within-task executive demands of Twenty Questions, but that their inefficiency in strategy relates to planning processes and question selection pretask. The implications for understanding ASD problem-solving skills and their impact on everyday functioning are discussed.

Mutual exclusivity in autism spectrum disorders: testing the pragmatic hypothesis

While there is ample evidence that children treat words as mutually exclusive, the cognitive basis of this bias is widely debated. We focus on the distinction between pragmatic and lexical constraints accounts. High-functioning children with autism spectrum disorders (ASD) offer a unique perspective on this debate, as they acquire substantial vocabularies despite impoverished social-pragmatic skills. We tested children and adolescents with ASD in a paradigm examining mutual exclusivity for words and facts. Words were interpreted contrastively more often than facts. Word performance was associated with vocabulary size; fact performance was associated with social-communication skills. Thus mutual exclusivity does not appear to be driven by pragmatics, suggesting that it is either a lexical constraint or a reflection of domain-general learning processes.

The intense world theory - a unifying theory of the neurobiology of autism

Autism covers a wide spectrum of disorders for which there are many views, hypotheses and theories. Here we propose a unifying theory of autism, the Intense World Theory. The proposed neuropathology is hyper-functioning of local neural microcircuits, best characterized by hyper-reactivity and hyper-plasticity. Such hyper-functional microcircuits are speculated to become autonomous and memory trapped leading to the core cognitive consequences of hyper-perception, hyper-attention, hyper-memory and hyper-emotionality. The theory is centered on the neocortex and the amygdala, but could potentially be applied to all brain regions. The severity on each axis depends on the severity of the molecular syndrome expressed in different brain regions, which could uniquely shape the repertoire of symptoms of an autistic child. The progression of the disorder is proposed to be driven by overly strong reactions to experiences that drive the brain to a hyper-preference and overly selective state, which becomes more extreme with each new experience and may be particularly accelerated by emotionally charged experiences and trauma. This may lead to obsessively detailed information processing of fragments of the world and an involuntarily and systematic decoupling of the autist from what becomes a painfully intense world. The autistic is proposed to become trapped in a limited, but highly secure internal world with minimal extremes and surprises. We present the key studies that support this theory of autism, show how this theory can better explain past findings, and how it could resolve apparently conflicting data and interpretations. The theory also makes further predictions from the molecular to the behavioral levels, provides a treatment strategy and presents its own falsifying hypothesis.

The timing and specificity of prenatal immune risk factors for autism modeled in the mouse and relevance to schizophrenia

Autism is a highly heritable condition, but there is strong epidemiological evidence that environmental factors, especially prenatal exposure to immune challenge, contribute to it. This evidence is largely indirect, and experimental testing is necessary to directly examine causal mechanisms. Mouse models reveal that prenatal immune perturbation disrupts postnatal brain maturation with alterations in gene and protein expression, neurotransmitter function, brain structure and behavioral indices reminiscent of, but not specific to, autism. This likely reflects a neurodevelopmental spectrum in which autism and schizophrenia share numerous genetic and environmental risk factors for difficulties in social interaction, communication, emotion processing and executive function. Recent epidemiological studies find that early rather than late pregnancy infection confers the greater risk of schizophrenia. The autism literature is more limited, but exposures in the 2nd half of pregnancy may be important. Mouse models of prenatal immune challenge help dissect these observations and show some common consequences of early and late gestational exposures, as well as distinct ramifications potentially relevant to schizophrenia and autism. Although nonspecificity of immune-stimulated mouse models could be considered a disadvantage, we propose a broadened perspective, exploiting the possibility that advances made investigating a target condition can contribute towards the understanding of related conditions.

Working memory in early-school-age children with Asperger's syndrome

Using a battery of working memory span tasks and n-back tasks, this study aimed to explore working memory functions in early-school-age children with Asperger's syndrome (AS). Twelve children with AS and 29 healthy children matched on age and IQ were recruited. Results showed: (a) children with AS performed better in digit and word recall tasks, but worse in block recall task and variant-visual-patterns test; (b) children with AS took longer time in most conditions of n-back tasks, and showed larger effects of task load. These findings indicated imbalance of working memory development in AS children: they had advantage in the phonological loop storing, but disadvantage in the visuospatial sketchpad storing, and partial deficit in central executive.

Neurobehavioral abnormalities in first-degree relatives of individuals with autism

CONTEXT

Studying sensorimotor and neurocognitive impairments in unaffected family members of individuals with autism may help identify familial pathophysiological mechanisms associated with the disorder.

OBJECTIVE

To determine whether atypical sensorimotor or neurocognitive characteristics associated with autism are present in first-degree relatives of individuals with autism.

DESIGN

Case-control comparison of neurobehavioral functions.

SETTING

University medical center.

PARTICIPANTS

Fifty-seven first-degree relatives of individuals with autism and 40 age-, sex-, and IQ-matched healthy control participants (aged 8-54 years).

MAIN OUTCOME MEASURES

Oculomotor tests of sensorimotor responses (saccades and smooth pursuit); procedural learning and response inhibition; neuropsychological tests of motor, memory, and executive functions; and psychological measures of social behavior, communication skills, and obsessive-compulsive behaviors.

RESULTS

On eye movement testing, family members demonstrated saccadic hypometria, reduced steady-state pursuit gain, and a higher rate of voluntary response inhibition errors relative to controls. They also showed lateralized deficits in procedural learning and open-loop pursuit gain (initial 100 milliseconds of pursuit) and increased variability in the accuracy of large-amplitude saccades that were confined to rightward movements. In neuropsychological studies, only executive functions were impaired relative to those of controls. Family members reported more communication abnormalities and obsessive-compulsive behaviors than controls. Deficits across oculomotor, neuropsychological, and psychological domains were relatively independent from one another.

CONCLUSIONS

Family members of individuals with autism demonstrate oculomotor abnormalities implicating pontocerebellar and frontostriatal circuits and left-lateralized alterations of frontotemporal circuitry and striatum. The left-lateralized alterations have not been identified in other neuropsychiatric disorders and are of interest given atypical brain lateralization and language development associated with the disorder. Similar oculomotor deficits have been reported in individuals with autism, suggesting that they may be familial and useful for studies of neurophysiological and genetic mechanisms in autism.

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.

The mind of the mnemonists: an MEG and neuropsychological study of autistic memory savants

About 10% of autistic individuals exhibit some form of islets of abilities in the face of serious intellectual or mental disability ("savant syndrome"). The aim of this study was to investigate brain mechanisms in a sample of autistic subjects with outstanding memory. We investigated seven mnemonist savants with high-functioning autism spectrum disorder and seven matched controls with 151-channel whole-head magnetencephalography in a continuous old-new paradigm. They were presented with 300 pseudowords and 300 shapes and had to indicate by button press, whether the presented stimulus had been shown before. Unexpectedly, mnemonist savants did not perform better than controls, but were outperformed in the recognition of pseudowords. Accordingly, event-related magnetic fields elicited by pseudowords showed widespread old-new effects in controls, but not in savants. A source analysis of its early components revealed right occipital activation in savants, but left parietal activation in controls. This might be related to a visual processing style in mnemonist savants that proved to be inefficient in this task. During the possibly familiarity-based recognition of shapes, there were earlier and more widespread bilateral old-new effects in mnemonist savants, what might reflect their experience with figural material. In a neuropsychological test battery, mnemonist savants performed comparably to autistic people without special memory skills. However, a different factor structure of these tests pointed to a different organization of memory in mnemonist savants compared to controls that is characterized by its relative independence of general intelligence.

Communication, interventions, and scientific advances in autism: a commentary

Autism spectrum disorders (ASD) affect approximately 1 in 150 children across the U.S., and are characterized by abnormal social actions, language difficulties, repetitive or restrictive behaviors, and special interests. ASD include autism (autistic disorder), Asperger Syndrome, and Pervasive Developmental Disorder not otherwise specified (PDD-NOS or atypical autism). High-functioning individuals may communicate with moderate-to-high language skills, although difficulties in social skills may result in communication deficits. Low-functioning individuals may have severe deficiencies in language, resulting in poor communication between the individual and others. Behavioral intervention programs have been developed for ASD, and are frequently adjusted to accommodate specific individual needs. Many of these programs are school-based and aim to support the child in the development of their skills, for use outside the classroom with family and friends. Strides are being made in understanding the factors contributing to the development of ASD, particularly the genetic contributions that may underlie these disorders. Mutant mouse models provide powerful research tools to investigate the genetic factors associated with ASD and its co-morbid disorders. In support, the BTBR T+tf/J mouse strain incorporates ASD-like social and communication deficits and high levels of repetitive behaviors. This commentary briefly reviews the reciprocal relationship between observations made during evidence-based behavioral interventions of high- versus low-functioning children with ASD and the accumulating body of research in autism, including animal studies and basic research models. This reciprocity is one of the hallmarks of the scientific method, such that research may inform behavioral treatments, and observations made during treatment may inform subsequent research.

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.

Brief report: are children with autism proficient word learners?

Many approaches to word learning argue for the importance of joint attention and other social-pragmatic abilities. This study explored word learning in children with autism (CWA), by examining it in ostensive and non-ostensive contexts, tested through both comprehension and elicited production. Novel nouns were taught to 17 CWA and 13 children with moderate learning difficulties (MLD) using an adapted version of Tomasello and Barton's (Developmental Psychology, 30: 639-650, 1994) search paradigm. In elicited production for words learnt within an ostensive context, CWA performed at a significantly higher level than MLD children. This is contrary to prior findings and suggests that word learning abilities in CWA have been underestimated.

Working memory in children with developmental disorders

The aim of the present study was to directly compare working memory skills across students with different developmental disorders to investigate whether the uniqueness of their diagnosis would impact memory skills. The authors report findings confirming differential memory profiles on the basis of the following developmental disorders: Specific Language Impairment, Developmental Coordination Disorder (DCD), Attention-Deficit/Hyperactivity Disorder, and Asperger syndrome (AS). Specifically, language impairments were associated with selective deficits in verbal short-term and working memory, whereas motor impairments (DCD) were associated with selective deficits in visuospatial short-term and working memory. Children with attention problems were impaired in working memory in both verbal and visuospatial domains, whereas the children with AS had deficits in verbal short-term memory but not in any other memory component. The implications of these findings are discussed in light of support for learning.

Theory of mind and verbal working memory deficits in parents of autistic children

The objective of this study was to investigate the potential values of executive function and social cognition deficits as endophenotypes of autism. While theory of mind (ToM) is generally accepted as a unitary concept, some have suggested that ToM may be separated into two components (mental state reasoning and decoding). In this study, both aspects of ToM and verbal working memory abilities were investigated with relatively demanding tasks. The authors used a neurocognitive battery to compare the executive function and social cognition skills of 76 parents of autistic probands with 41 parents of healthy children. Both groups were matched for IQ, age and gender. Index parents had verbal working memory deficits. They had also low performance on a mental state reasoning task. Index parents had difficulties in reasoning about others' emotions. In contrast to findings in the control group, low performance of mental state reasoning ability was not associated with working memory deficit in index parents. Social cognition and working memory impairments may represent potential endophenotypes, related to an underlying vulnerability for autistic spectrum disorders.

Understanding executive control in autism spectrum disorders in the lab and in the real world

In this paper, we review the most recent and often conflicting findings on conventional measures of executive control in autism spectrum disorders. We discuss the obstacles to accurate measurement of executive control, such as: its prolonged developmental trajectory; lack of consensus on its definition and whether it is a unitary construct; the inherent complexity of executive control; and the difficulty measuring executive-control functions in laboratory or clinical settings. We review the potential of an ecological-validity framework to address some of these problems, and describe new tests claiming verisimilitude, or close resemblance to "real life" demands. We also review the concept of veridicality, which allows for the measurement of the ecological validity of any task, and discuss the few studies addressing ecological validity in individuals with autism. Our review suggests that a multi-source approach emphasizing veridicality may provide the most comprehensive assessment of executive control in autism.

Verbal Working Memory and Story Retelling in School-Age Children With Autism

Purpose

This study examined verbal working memory and language ability in 15 school-age children with autism using 3 verbal working memory tasks and 1 story recall task.

Method

Three measures of verbal working memory—nonword repetition, memory for digits span, and sentence imitation—were given to children with autism and age-matched controls. Verbal working memory measures were chosen to reflect increasing levels of cognitive–linguistic complexity. Story retelling was measured using The Renfrew Bus Story (J. Cowley & C. Glasgow, 1994) and was scored for the percentage of propositions recalled and the average utterance length.

Results

A profile of verbal working memory deficits was seen in children with autism, with poorer performance on more complex verbal memory tasks. Performance on the 3 verbal memory tasks was independent of articulation ability. For the group with autism, receptive vocabulary was associated with sentence imitation and story recall but not with nonword repetition or digits span. Sentence imitation was related to story recall, but the relationship disappeared when the effect of vocabulary was removed.

Conclusions

Vocabulary and language processing demands affect the performance of children with autism on tasks of verbal memory and story retelling. Results are viewed within a connectionist framework of verbal working memory .

Cognitive control in autism spectrum disorders

Cognitive control refers to the ability to flexibly allocate mental resources to guide thoughts and actions in light of internal goals. Given the behavioral inflexibility exhibited by individuals with autism spectrum disorders (ASDs), it would appear they experience cognitive control deficits. Cognitive correlates of this behavioral inflexibility have been elusive in previous investigations. Study goals were to investigate deficits in cognitive control in ASDs; to explore its developmental trajectory; and to test whether control deficits are related to symptoms of inflexible thoughts and/or behaviors, and attention symptoms. Thirty-one children and adolescents aged 8-17 with ASDs and 32 age, IQ, and gender matched control subjects completed cognitive, diagnostic, and behavorial assessments, as well as a measure of cognitive control involving overcoming a prepotent response tendency. Compared with typically developing control subjects, individuals with ASDs exhibited deficits in cognitive control. Younger children with ASDs did not demonstrate age-related improvements in cognitive control. Modest relationships between cognitive control, IQ, and attention problems were found for the sample. Only the relationship between cognitive control and full-scale IQ survived correction for multiple comparisons.

Identification and evaluation of children with autism spectrum disorders

Autism spectrum disorders are not rare; many primary care pediatricians care for several children with autism spectrum disorders. Pediatricians play an important role in early recognition of autism spectrum disorders, because they usually are the first point of contact for parents. Parents are now much more aware of the early signs of autism spectrum disorders because of frequent coverage in the media; if their child demonstrates any of the published signs, they will most likely raise their concerns to their child's pediatrician. It is important that pediatricians be able to recognize the signs and symptoms of autism spectrum disorders and have a strategy for assessing them systematically. Pediatricians also must be aware of local resources that can assist in making a definitive diagnosis of, and in managing, autism spectrum disorders. The pediatrician must be familiar with developmental, educational, and community resources as well as medical subspecialty clinics. This clinical report is 1 of 2 documents that replace the original American Academy of Pediatrics policy statement and technical report published in 2001. This report addresses background information, including definition, history, epidemiology, diagnostic criteria, early signs, neuropathologic aspects, and etiologic possibilities in autism spectrum disorders. In addition, this report provides an algorithm to help the pediatrician develop a strategy for early identification of children with autism spectrum disorders. The accompanying clinical report addresses the management of children with autism spectrum disorders and follows this report on page 1162 [available at www.pediatrics.org/cgi/content/full/120/5/1162]. Both clinical reports are complemented by the toolkit titled "Autism: Caring for Children With Autism Spectrum Disorders: A Resource Toolkit for Clinicians," which contains screening and surveillance tools, practical forms, tables, and parent handouts to assist the pediatrician in the identification, evaluation, and management of autism spectrum disorders in children.

Fronto-limbic functioning in children and adolescents with and without autism

We used neuropsychological tasks to investigate integrity of brain circuits linking orbitofrontal cortex and amygdala (orbitofrontal-amygdala), and dorsolateral prefrontal cortex and hippocampus (dorsolateral prefrontal-hippocampus), in 138 individuals aged 7-18 years, with and without autism. We predicted that performance on orbitofrontal-amygdala tasks would be poorer in the Autism group compared to the Non-Autism group regardless of intellectual level (verbal mental age, VMA) and that performance on dorsolateral prefrontal-hippocampus tasks would be associated primarily with intellectual level. Predicted differences between Autism and Non-Autism groups on orbitofrontal-amygdala tasks were present but greater in individuals with higher VMA. On dorsolateral prefrontal-hippocampus tasks, poorer performance by the Autism compared to the Non-Autism group was found at all VMA levels. Group differences suggest both brain circuits are impaired in autism, but performance on all tasks is also associated with intellectual level.

Maturation of executive function in autism

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Detection and mapping of hippocampal abnormalities in autism

Brain imaging studies of the hippocampus in autism have yielded inconsistent results. In this study, a computational mapping strategy was used to examine the three-dimensional profile of hippocampal abnormalities in autism. Twenty-one males with autism (age: 9.5+/-3.3 years) and 24 male controls (age: 10.3+/-2.4 years) underwent a volumetric magnetic resonance imaging scan at 3 Tesla. The hippocampus was delineated, using an anatomical protocol, and hippocampal volumes were compared between the two groups. Hippocampal traces were also converted into three-dimensional parametric surface meshes, and statistical brain maps were created to visualize morphological differences in the shape and thickness of the hippocampus between groups. Parametric surface meshes and shape analysis revealed subtle differences between patients and controls, particularly in the right posterior hippocampus. These deficits were significant even though the groups did not differ significantly with traditional measures of hippocampal volume. These results suggest that autism may be associated with subtle regional reductions in the size of the hippocampus. The increased statistical and spatial power of computational mapping methods provided the ability to detect these differences, which were not found with traditional volumetric methods.

The profile of memory function in children with autism

A clinical memory test was administered to 38 high-functioning children with autism and 38 individually matched normal controls, 8-16 years of age. The resulting profile of memory abilities in the children with autism was characterized by relatively poor memory for complex visual and verbal information and spatial working memory with relatively intact associative learning ability, verbal working memory, and recognition memory. A stepwise discriminant function analysis of the subtests found that the Finger Windows subtest, a measure of spatial working memory, discriminated most accurately between the autism and normal control groups. A principal components analysis indicated that the factor structure of the subtests differed substantially between the children with autism and controls, suggesting differing organizations of memory ability.

Functional connectivity in an fMRI working memory task in high-functioning autism

An fMRI study was used to measure the brain activation of a group of adults with high-functioning autism compared to a Full Scale and Verbal IQ and age-matched control group during an n-back working memory task with letters. The behavioral results showed comparable performance, but the fMRI results suggested that the normal controls might use verbal codes to perform the task, while the adults with autism might use visual codes. The control group demonstrated more activation in the left than the right parietal regions, whereas the autism group showed more right lateralized activation in the prefrontal and parietal regions. The autism group also had more activation than the control group in the posterior regions including inferior temporal and occipital regions. The analysis of functional connectivity yielded similar patterns for the two groups with different hemispheric correlations. The temporal profile of the activity in the prefrontal regions was more correlated with the left parietal regions for the control group, whereas it was more correlated with the right parietal regions for the autism group.