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.
Autism; Set shifting; Dimension-change card sort task; Repetitive behaviors; Executive functioning; Children
There has been considerable controversy regarding whether children with autism spectrum disorder (ASD) and typically developing children (TD) show different eye movement patterns when processing faces. We investigated ASD and age- and IQ-matched TD children's scanning of faces using a novel multi-method approach. We found that ASD children spent less time looking at the whole face generally. After controlling for this difference, ASD children's fixations of the other face parts, except for the eye region, and their scanning paths between face parts were comparable either to the age-matched or IQ-matched TD groups. In contrast, in the eye region, ASD children's scanning differed significantly from that of both TD groups: (a) ASD children fixated significantly less on the right eye (from the observer's view); (b) ASD children's fixations were more biased towards the left eye region; and (c) ASD children fixated below the left eye, whereas TD children fixated on the pupil region of the eye. Thus, ASD children do not have a general abnormality in face scanning. Rather, their abnormality is limited to the eye region, likely due to their strong tendency to avoid eye contact.
autism spectrum disorder; face processing; face recognition; eye movements; eye tracking
Eye tracking has been used to investigate gaze behaviours in individuals with autism spectrum disorder (ASD). However, traditional analysis has yet to find behavioural characteristics shared by both children and adults with ASD. To distinguish core ASD gaze behaviours from those that change with development, we examined temporo-spatial gaze patterns in children and adults with and without ASD while they viewed video clips. We summarized the gaze patterns of 104 participants using multidimensional scaling so that participants with similar gaze patterns would cluster together in a two-dimensional plane. Control participants clustered in the centre, reflecting a standard gaze behaviour, whereas participants with ASD were distributed around the periphery. Moreover, children and adults were separated on the plane, thereby showing a clear effect of development on gaze behaviours. Post hoc frame-by-frame analyses revealed the following findings: (i) both ASD groups shifted their gaze away from a speaker earlier than the control groups; (ii) both ASD groups showed a particular preference for letters; and (iii) typical infants preferred to watch the mouth rather than the eyes during speech, a preference that reversed with development. These results highlight the importance of taking the effect of development into account when addressing gaze behaviours characteristic of ASD.
eye tracking; eye movements; autism; development; mouth viewing; turn taking
Because previous studies of attention in autism spectrum disorders (ASD) have been restricted in age range examined, little is known about how these processes develop over the course of childhood. In this study we examined cross-sectional age effects on patterns of visual attention to social and nonsocial information in 43 typically developing children and 51 children with ASD ranging in age from 2 to 18. Results indicated a sharp increase in visual exploration with age and a decrease in perseverative and detail-focused attention for both groups of children. However, increased age was associated with greater increases in visual exploration for typically developing children than for those children with ASD. The developmental differences were most pronounced for attention to certain nonsocial stimuli as children with ASD demonstrated a disproportionate attentional bias for these stimuli from very early in life. Disproportionate visual attention to certain nonsocial objects relative to social stimuli in ASD spanned from early to late childhood, and thus may represent both an early and a persistent characteristic of the disorder.
autism; attention; visual exploration; development; eye tracking
Children with Autism Spectrum Disorders (ASDs) are impaired in visually disengaging attention in both social and non-social contexts, impairments that may, in subtler form, also affect the infant siblings of children with an ASD (ASD-sibs). We investigated patterns of visual attention (gazing) in six-month-old ASD-sibs (n = 17) and the siblings of typically developing children (COMP-sibs; n =17) during the Face-to-Face/Still-Face Protocol (FFSF), in which parents are sequentially responsive, nonresponsive, and responsive to their infants. Throughout the protocol, ASD-sibs shifted their gaze to and from their parents' faces less frequently than did COMP-sibs. The mean durations of ASD-sibs’ gazes away from their parents' faces were longer than those of COMP-sibs. ASD-sibs and COMP-sibs did not differ in the mean durations of gazes at their parents' faces. In sum, ASD-sibs showed no deficits in visual interest to their parents’ faces, but greater interest than COMP-sibs in non-face stimuli.
autism spectrum disorders; siblings; at-risk; disengagement; early deficits
The Dimensional Change Card Sort (DCCS) task requires children to switch from sorting cards based on shape or color to sorting based on the other dimension. Typically, 3-year-olds perseverate, while 4-year-olds flexibly sort by different dimensions. Zelazo et al. (1996) asked children questions about the post-switch rules and found an apparent dissociation between rule-knowledge and rule-use: 3-year-olds demonstrate accurate knowledge of the post-switch rules despite sorting cards incorrectly. Here, we show that children’s success with these questions is grounded in their use of available visual cues: children who fail sorting use the target cards to correctly answer questions; when the cards are unavailable, they guess. This suggests that there may not be a dissociation between children’s rule-knowledge and rule-use in the DCCS.
Impaired neuropsychological test performance, especially on tests of executive function and attention, is often seen in children diagnosed with autism spectrum disorders (ASD). Structures involved in fronto-striatal circuitry, such as the caudate nucleus, may support these cognitive abilities. However, few studies have examined caudate volumes specifically in children with ASD, or correlated caudate volumes to cognitive ability.
Neuropsychological test scores and caudate volumes of children with ASD were compared to those of children with bipolar disorder (BD) and of typically developing (TD) children. The relationship between test performance and caudate volumes was analyzed.
The ASD group displayed larger right and left caudate volumes, and modest executive deficits, compared to TD controls. While caudate volume inversely predicted performance on the Wisconsin Card Sorting Test in all participants, it differentially predicted performance on measures of attention across the ASD, BD and TD groups.
Larger caudate volumes were related to impaired problem solving. On a test of attention, larger left caudate volumes predicted increased impulsivity and more omission errors in the ASD group as compared to the TD group, however smaller volume predicted poorer discriminant responding as compared to the BD group.
executive function; attention; bipolar disorder; autism spectrum disorders; caudate volume; neuroimaging
To explore mechanisms underlying reduced fixation of eyes in autism, children with Autistic Spectrum Disorders (ASD) and typically developing children were tested in five visual search experiments: simple color feature; color-shape conjunction; face in non-face objects; mouth region; and eye region. No group differences were found for reaction time profile shapes in any of the five experiments, suggesting intact basic search mechanics in children with ASD. Contrary to early reports in the literature, but consistent with other more recent findings, we observed no superiority for conjunction search in children with ASD. Importantly, children with ASD did show reduced accuracy for eye region search (p = .005), suggesting that eyes contribute less to high-level face representations in ASD or that there is an eye region-specific disruption to attentional processes engaged by search in ASD.
Previous research suggests that many individuals with autism spectrum disorder (ASD) have impaired facial identity recognition, and also exhibit abnormal visual scanning of faces. Here, two hypotheses accounting for an association between these observations were tested: i) better facial identity recognition is associated with increased gaze time on the Eye region; ii) better facial identity recognition is associated with increased eye-movements around the face.
Methodology and Principal Findings
Eye-movements of 11 children with ASD and 11 age-matched typically developing (TD) controls were recorded whilst they viewed a series of faces, and then completed a two alternative forced-choice recognition memory test for the faces. Scores on the memory task were standardized according to age. In both groups, there was no evidence of an association between the proportion of time spent looking at the Eye region of faces and age-standardized recognition performance, thus the first hypothesis was rejected. However, the ‘Dynamic Scanning Index’ – which was incremented each time the participant saccaded into and out of one of the core-feature interest areas – was strongly associated with age-standardized face recognition scores in both groups, even after controlling for various other potential predictors of performance.
Conclusions and Significance
In support of the second hypothesis, results suggested that increased saccading between core-features was associated with more accurate face recognition ability, both in typical development and ASD. Causal directions of this relationship remain undetermined.
Dysfunctions of the prefrontal cortex have been previously reported in individuals with autism spectrum disorders (ASD). Previous studies reported that first-degree relatives of individuals with ASD show atypical brain activity during tasks associated with social function. However, developmental changes in prefrontal dysfunction in ASD and genetic influences on the phenomena remain unclear. In the present study, we investigated the change in hemoglobin concentration in the prefrontal cortex as measured with near-infrared spectroscopy, in children and adults with ASD during the letter fluency test. Moreover, to clarify the genetic influences on developmental changes in the prefrontal dysfunction in ASD, unaffected siblings of the ASD participants were also assessed.
Study participants included 27 individuals with high-functioning ASD, age- and IQ-matched 24 healthy non-affected siblings, and 27 unrelated healthy controls aged 5 to 39 years. The relative concentration of hemoglobin ([Hb]) in the prefrontal cortex was measured during the letter fluency task. For children, neither the [oxy-Hb] change during the task nor task performances differed significantly among three groups. For adults, the [oxy-Hb] increases during the task were significantly smaller in the bilateral prefrontal cortex in ASD than those in control subjects, although task performances were similar. In the adult siblings the [oxy-Hb] change was intermediate between those in controls and ASDs.
Although indirectly due to a cross-sectional design, the results of this study indicate altered age-related change of prefrontal activity during executive processing in ASD. This is a first near-infrared spectroscopy study that implies alteration in the age-related changes of prefrontal activity in ASD and genetic influences on the phenomena.
Children with autism spectrum disorders (ASDs) show daily cognitive flexibility deficits, but laboratory data are unconvincing. The current study aimed to bridge this gap. Thirty-one children with ASD (8–12 years) and 31 age- and IQ-matched typically developing children performed a gender emotion switch task. Unannounced switches and complex stimuli (emotional faces) improved ecological validity; minimal working memory-load prevented bias in the findings. Overall performance did not differ between groups, but in a part of the ASD group performance was slow and inaccurate. Moreover, within the ASD group switching from emotion to gender trials was slower than vice versa. Children with ASD do not show difficulties on an ecological valid switch task, but have difficulty disengaging from an emotional task set.
ASD; Task switching; Cognitive flexibility; Emotion; Executive functioning
Assessment of anxiety symptoms in autism spectrum disorders (ASD) is a challenging task due to the symptom overlap between the two conditions as well as the difficulties in communication and awareness of emotions in ASD. This motivates the development of a physiological marker of anxiety in ASD that is independent of language and does not require observation of overt behaviour. In this study, we investigated the feasibility of using indicators of autonomic nervous system (ANS) activity for this purpose. Specially, the objectives of the study were to 1) examine whether or not anxiety causes significant measurable changes in indicators of ANS in an ASD population, and 2) characterize the pattern of these changes in ASD. We measured three physiological indicators of the autonomic nervous system response (heart rate, electrodermal activity, and skin temperature) during a baseline (movie watching) and anxiety condition (Stroop task) in a sample of typically developing children (n = 17) and children with ASD (n = 12). The anxiety condition caused significant changes in heart rate and electrodermal activity in both groups, however, a differential pattern of response was found between the two groups. In particular, the ASD group showed elevated heart rate during both baseline and anxiety conditions. Elevated and blunted phasic electrodermal activity were found in the ASD group during baseline and anxiety conditions, respectively. Finally, the ASD group did not show the typical decrease in skin temperature in response to anxiety. These results suggest that 1) signals of the autonomic nervous system may be used as indicators of anxiety in children with ASD, and 2) ASD may be associated with an atypical autonomic response to anxiety that is most consistent with sympathetic over-arousal and parasympathetic under-arousal.
Functional magnetic resonance imaging (fMRI) and functional connectivity MRI (fcMRI) studies of autism spectrum disorders (ASD) have suggested atypical patterns of activation and long-distance connectivity for diverse tasks and networks in ASD. We explored the regional homogeneity (ReHo) approach in ASD, which is analogous to conventional fcMRI, but focuses on local connectivity. FMRI data of 26 children with ASD and 29 typically developing (TD) children were acquired during continuous task performance (visual search). Effects of motion and task were removed and Kendall‟s coefficient of concordance (KCC) was computed, based on the correlation of the blood oxygen level dependent (BOLD) time series for each voxel and its 6 nearest neighbors. ReHo was lower in the ASD than the TD group in superior parietal and anterior prefrontal regions. Inverse effects of greater ReHo in the ASD group were detected in lateral and medial temporal regions, predominantly in the right hemisphere. Our findings suggest that ReHo is a sensitive measure for detecting cortical abnormalities in autism. However, impact of methodological factors (such as spatial resolution) on ReHo require further investigation.
Autism Spectrum Disorder; functional MRI; functional connectivity; regional homogeneity
This study used eye-tracking methodology to assess audiovisual (AV) speech perception in 26 children ranging in age from 5-15 years, half with autism spectrum disorders (ASD) and half with typical development (TD). Given the characteristic reduction in gaze to the faces of others in children with ASD, it was hypothesized that they would show reduced influence of visual information on heard speech. Responses were compared on a set of auditory, visual and audiovisual speech perception tasks. Even when fixated on the face of the speaker, children with ASD were less visually influenced than TD controls. This indicates fundamental differences in the processing of AV speech in children with ASD, which may contribute to their language and communication impairments.
Plaisted, O’Riordan and colleagues (Plaisted, O’Riordan & Baron-Cohen, 1998; O’Riordan, 2004) showed that school-age children and adults with Autism Spectrum Disorder (ASD) are faster at finding targets in certain types of visual search tasks than typical controls. Currently though, there is very little known about the visual search skills of very young children (1–3-year-olds) – both typically developing or with ASD. We used an eye-tracker to measure looking behavior, providing fine-grained measures of visual search in 2.5-year-old toddlers with and without ASD (this representing the age by which many children may first receive a diagnosis of ASD). Importantly, our paradigm required no verbal instructions or feedback, making the task appropriate for toddlers who are pre- or nonverbal. We found that toddlers with ASD were more successful at finding the target than typically developing, age-matched controls. Further, our paradigm allowed us to estimate the number of items scrutinized per trial, revealing that for large set size conjunctive search, toddlers with ASD scrutinized as many as twice the number of items as typically developing toddlers, in the same amount of time.
Children with pervasive developmental disorders (PDD), such as children with autism spectrum disorders (ASD), often show auditory processing deficits related to their overarching language impairment. Auditory training programs such as Fast ForWord Language may potentially alleviate these deficits through training-induced improvements in auditory processing.
To assess the impact of auditory training on auditory function in children with ASD, brainstem and cortical responses to speech sounds presented in quiet and noise were collected from five children with ASD who completed Fast ForWord training.
Relative to six control children with ASD who did not complete Fast ForWord, training-related changes were found in brainstem response timing (three children) and pitch-tracking (one child), and cortical response timing (all five children) after Fast ForWord use.
These results provide an objective indication of the benefit of training on auditory function for some children with ASD.
A subset of individuals with autism spectrum disorder (ASD) performs more proficiently on certain visual tasks than may be predicted by their general cognitive performances. However, in younger children with ASD (aged 5 to 7), preserved ability in these tasks and the neurophysiological correlates of their ability are not well documented. In the present study, we used a custom child-sized magnetoencephalography system and demonstrated that preserved ability in the visual reasoning task was associated with rightward lateralisation of the neurophysiological connectivity between the parietal and temporal regions in children with ASD. In addition, we demonstrated that higher reading/decoding ability was also associated with the same lateralisation in children with ASD. These neurophysiological correlates of visual tasks are considerably different from those that are observed in typically developing children. These findings indicate that children with ASD have inherently different neural pathways that contribute to their relatively preserved ability in visual tasks.
Minshew and Goldstein (1998) postulated that autism spectrum disorder (ASD) is a disorder of complex information processing. The current study was designed to investigate this hypothesis. Participants with and without ASD completed two scene perception tasks: a simple “spot the difference” task, where they had to say which one of a pair of pictures had a detail missing, and a complex “which one's weird” task, where they had to decide which one of a pair of pictures looks “weird”. Participants with ASD did not differ from TD participants in their ability to accurately identify the target picture in both tasks. However, analysis of the eye movement sequences showed that participants with ASD viewed scenes differently from normal controls exclusively for the complex task. This difference in eye movement patterns, and the method used to examine different patterns, adds to the knowledge base regarding eye movements and ASD. Our results are in accordance with Minshew and Goldstein's theory that complex, but not simple, information processing is impaired in ASD.
Impaired motor coordination is prevalent in children with Autism Spectrum Disorders (ASD) and affects adaptive skills. Little is known about the development of motor patterns in young children with ASD between 2 and 6 years of age. The purpose of the current study was threefold: (1) to describe developmental correlates of motor coordination in children with ASD, (2) to identify the extent to which motor coordination deficits are unique to ASD by using a control group of children with other developmental disabilities (DD), and (3) to determine the association between motor coordination variables and functional fine motor skills. Twenty-four children with ASD were compared to 30 children with typical development (TD) and 11 children with DD. A precision grip task was used to quantify and analyze motor coordination. The motor coordination variables were two temporal variables (grip to load force onset latency and time to peak grip force) and two force variables (grip force at onset of load force and peak grip force). Functional motor skills were assessed using the Fine Motor Age Equivalents of the Vineland Adaptive Behavior Scale and the Mullen Scales of Early Learning. Mixed regression models were used for all analyses. Children with ASD presented with significant motor coordination deficits only on the two temporal variables, and these variables differentiated children with ASD from the children with TD, but not from children with DD. Fine motor functional skills had no statistically significant associations with any of the motor coordination variables. These findings suggest that subtle problems in the timing of motor actions, possibly related to maturational delays in anticipatory feed-forward mechanisms, may underlie some motor deficits reported in children with ASD, but that these issues are not unique to this population. Further research is needed to investigate how children with ASD or DD compensate for motor control deficits to establish functional skills.
autism spectrum disorders; developmental delay; motor deficits; motor coordination; temporal motor coordination; precision grip; grip force; load force
Autism spectrum disorder (ASD) has been associated with decreased coherent dot motion (CDM) performance, a task that measures magnocellular sensitivity as well as fronto-parietal attentional integration processing. In order to clarify the role of spatial attention in CDM tasks, we measured the perception of coherently moving dots displayed in the central or peripheral visual field in ASD and typically developing children. A dorsal-stream deficit in children with ASD should predict a generally poorer performance in both conditions. In our study, however, we show that in children with ASD, CDM perception was selectively impaired in the central condition. In addition, in the ASD group, CDM efficiency was correlated to the ability to zoom out the attentional focus. Importantly, autism symptoms severity was related to both the CDM and attentional zooming-out impairment. These findings suggest that a dysfunction in the attentional network might help to explain decreased CDM discrimination as well as the “core” social cognition deficits of ASD.
Autism Spectrum Disorders (ASD) are associated with abnormalities in face memory, which evidence suggests has a protracted development through adolescence. The development of face memory in people with and without ASD, from 9 to 29 years old, was examined using the Cambridge Face Memory Test (CFMT). Results indicate that the developmental improvement evident from adolescence to adulthood typically was not apparent in individuals with ASD. While children and adolescents with ASD performed similarly to typically developing individuals comparable in age and IQ, adults with ASD displayed limitations on the CFMT. The pattern of performance was constant across conditions despite differences in the timing of the presentation and delay. This atypical development in ASD is consistent with the view that the processing of complex visual stimuli continues to develop through adolescence, along with the function and structure of the temporal lobes, but that this process is disrupted in ASD. This result underscores the importance of characterizing adolescent development for understanding ASD, and suggests additional opportunities for intervention.
development; developmental disorders; frontal; temporal; social cognition
Individuals diagnosed with autism spectrum disorder (ASD) exhibit lifelong abnormalities in the adaptive allocation of visual attention. The ubiquitous nature of attentional impairments in ASD has led some authors to hypothesize that atypical attentional modulation may be a factor in the development of higher-level sociocommunicative deficits.
Participants were 20 children with ASD and 20 age- and Nonverbal IQ-matched typically developing (TD) children. We used the Attention Network Test (ANT) to investigate the efficiency and independence of three discrete attentional networks: alerting, orienting, and executive control. Additionally, we sought to investigate the relationship between each attentional network and measures of sociocommunicative symptom severity in children with ASD.
Results indicate that the orienting, but not alerting or executive control, networks may be impaired in children with ASD. In contrast to TD children, correlational analyses suggest that the alerting and executive control networks may not function as independently in children with ASD. Additionally, an association was found between the alerting network and social impairment and between the executive control network and IQ in children with ASD.
The results provide further evidence of an impairment in the visuospatial orienting network in ASD and suggest that there may be greater interdependence of alerting and executive control networks in ASD. Furthermore, decreased ability to efficiently modulate levels of alertness was related to increased sociocommunicative deficits, suggesting that domain-general attentional function may be associated with ASD symptomatology.
Autism; reaction time; visual attention; alerting; orienting; executive control
Prior studies suggest that autism spectrum disorders (ASD) are associated with a domain-specific memory impairment for faces. The underlying cause of this problem and its relation to impaired visual scanning of faces—particularly of the eyes—remains to be determined. We recorded eye movements while 22 high-functioning ASD and 21 typically developing (TD) adolescents encoded and later recognized faces and objects from a single, nonsocial object category (electric fans). Relative to TD subjects, ASD individuals had poorer memory for faces, but not fans. Correlational analyses showed significant relationships between recognition memory and fixations. Eye tracking during encoding revealed that TD subjects made more fixations to faces than fans, whereas ASD individuals did not differ in number of fixations made to each stimulus type. Moreover, although both the TD and ASD groups showed a strong preference for fixating the eyes more than the mouth, the ASD subjects were less likely than TD subjects to scan regions of the face outside of the primary facial features (i.e., eyes, nose, and mouth). We concluded that ASD individuals have a domain-specific memory impairment for faces relative to mechanical objects and that this impairment may be related to abnormal scanning during encoding.
Autistic disorder; Asperger’s syndrome; Face processing; Memory; Eye tracking; Domain-specificity
Autism spectrum disorder (ASD) is a severe neuropsychiatric disorder which has complex pathobiology with profound influences of genetic factors in its development. Although the numerous autism susceptible genes were identified, the etiology of autism is not fully explained. Using DNA microarray, we examined gene expression profiling in peripheral blood from 21 individuals in each of the four groups; young adults with ASD, age- and gender-matched healthy subjects (ASD control), healthy mothers having children with ASD (asdMO), and asdMO control. There was no blood relationship between ASD and asdMO. Comparing the ASD group with control, 19 genes were found to be significantly changed. These genes were mainly involved in cell morphology, cellular assembly and organization, and nerve system development and function. In addition, the asdMO group possessed a unique gene expression signature shown as significant alterations of protein synthesis despite of their nonautistic diagnostic status. Moreover, an ASD-associated gene expression signature was commonly observed in both individuals with ASD and asdMO. This unique gene expression profiling detected in peripheral leukocytes from affected subjects with ASD and unaffected mothers having ASD children suggest that a genetic predisposition to ASD may be detectable even in peripheral cells. Altered expression of several autism candidate genes such as FMR-1 and MECP2, could be detected in leukocytes. Taken together, these findings suggest that the ASD-associated genes identified in leukocytes are informative to explore the genetic, epigenetic, and environmental background of ASD and might become potential tools to assess the crucial factors related to the clinical onset of the disorder.
This study used eye-tracking to examine how 20-month old toddlers with autism spectrum disorder (ASD) (N=28), typical development (TD) (N=34), and non-autistic developmental delays (DD) (N=16) monitored the activities occurring in a context of an adult-child play interaction. Toddlers with ASD, in comparison to control groups, showed less attention to the activities of others and focused more on background objects (e.g. toys). In addition, while all groups spent the same time overall looking at people, toddlers with ASD looked less at people's heads and more at their bodies. In ASD, these patterns were associated with cognitive deficits and greater autism severity. These results suggest that the monitoring of the social activities of others is disrupted early in the developmental progression of autism, limiting future avenues for observational learning.
activity monitoring; autism; eye-tracking; joint attention; social learning; observational learning