Although autism is usually characterized with respect to sociocommunicative impairments, visual search is known as a domain of relative performance strength in this disorder. The present study used functional MRI during visual search in children with autism spectrum disorder (n = 19; mean age = 13;10) and matched typically developing children (n = 19; mean age = 14;0). We selected regions of interest within two attentional networks known to play a crucial role in visual search processes, such as goal-directed selective attention, filtering of irrelevant distractors, and detection of behaviorally-relevant information, and examined activation and connectivity within and between these attentional networks. Additionally, based on prior research suggesting links between visual search abilities and autism symptomatology, we tested for correlations between sociocommunicative impairments and behavioral and neural indices of search. Contrary to many previous functional connectivity magnetic resonance imaging studies of autism that reported functional underconnectivity for task domains of weakness, we found atypically increased connectivity within and between attentional networks in autism. Additionally, we found increased functional connectivity for occipital regions, both locally and for long-distance connections with frontal regions. Both behavioral and neural indices of search were correlated with sociocommunicative impairment in children with autism. This association suggests that strengths in non-social visuospatial processing may be related to the development of core autistic sociocommunicative impairments.

Although atypical eye gaze is commonly observed in autism, little is known about underlying oculomotor abnormalities. Our review of visual search and oculomotor systems in the healthy brain suggests that relevant networks may be partially impaired in autism, given regional abnormalities known from neuroimaging. However, direct oculomotor evidence for autism remains limited. This gap is critical since oculomotor abnormalities might play a causal role in functions known to be impaired in autism, such as imitation and joint attention. We integrate our oculomotor review into a developmental approach to language impairment related to nonverbal prerequisites. Oculomotor abnormalities may play a role as a sensorimotor defect at the root of impairments in later developing functional systems, ultimately resulting in sociocommunicative deficits.

Although previous studies have shown that individuals with autism spectrum disorder (ASD) excel at visual search, underlying neural mechanisms remain unknown. This study investigated the neurofunctional correlates of visual search in children with ASD and matched typically developing (TD) children, using an event-related functional magnetic resonance imaging design. We used a visual search paradigm, manipulating search difficulty by varying set size (6, 12, or 24 items), distractor composition (heterogeneous or homogeneous) and target presence to identify brain regions associated with efficient and inefficient search. While the ASD group did not evidence accelerated response time (RT) compared with the TD group, they did demonstrate increased search efficiency, as measured by RT by set size slopes. Activation patterns also showed differences between ASD group, which recruited a network including frontal, parietal, and occipital cortices, and the TD group, which showed less extensive activation mostly limited to occipito-temporal regions. Direct comparisons (for both homogeneous and heterogeneous search conditions) revealed greater activation in occipital and frontoparietal regions in ASD than in TD participants. These results suggest that search efficiency in ASD may be related to enhanced discrimination (reflected in occipital activation) and increased top-down modulation of visual attention (associated with frontoparietal activation).

The present study examined fixation frequency and duration during an EFT in an effort to better understand the attentional and perceptual processes by which individuals with ASD achieve accelerated EFT performance. In particular, we aimed to elucidate differences in the patterns of eyemovement in ASD and TD children, thus providing evidence relevant to the competing weak central coherence and enhanced perceptual functioning theories. Consistent with prior EFT studies, we found accelerated RT in children with ASD. No group differences were seen for fixation frequency, but the ASD group made significantly shorter fixations compared to TD group. Eye-movement results indicate that RT advantage in ASD is related to both weak central coherence and enhanced perceptual functioning. Keywordsautism; reaction time; visual attention; visual perception; eye movement; eye fixation Atypical visual-spatial perception in individuals with autism spectrum disorder (ASD) has been exemplified by enhanced performance on a variety of experimental tasks (see Dakin & Frith, 2005, for review , 2006). According to the WCC, accelerated performance during the EFT is a consequence of differences in implicit processing style; individuals with ASD perceive local parts, whereas typically developing (TD) individuals form a global percept before attending to the local elements of the global whole. Alternatively, Mottron and colleagues (2006) have proposed that accelerated EFT performance in ASD is the result of enhanced perceptual functioning (EPF). The EPF theory hypothesizes that local bias develops, not from a deficit in processing global information, but rather from superior low-level perceptual processes.The present study examined fixation frequency and duration during an EFT in an effort to better understand the attentional and perceptual processes by which children with ASD achieve accelerated performance. In particular, we aimed to elucidate differences in the patterns of eyemovement in ASD and TD children, thus providing evidence relevant to the competing WCC and EPF theories. We used a modified version of an EFT designed by Manjaly and colleagues (2007) which included both embedded figure and baseline perceptual control conditions. We hypothesized that response time (RT) increases in the test compared to the baseline condition would be less pronounced in ASD compared to TD children. A further hypothesis was prompted by a recent study by Kemner et al. (2007), who suggested that fewer and/or shorter fixations underlie enhanced visual search in ASD. Analogously, we hypothesized that superior EFT performance in ASD would be the result of a reduced number and/or duration of fixations. Methods ParticipantsFifteen school-age children with ASD and 11 TD children were recruited for the current study. Data from three children with ASD were incomplete due to noncompliance. The final sample thus included 12 children with ASD, all of whom met DSM-IV-TR (APA, 2000) criteria for autism spectrum disorder, and an age-and nonverbal IQ-matched...