The Neural Mechanisms Underlying Global and Local Information Processing in High-Functioning Children with Autism

Background:  A comprehensive account of the nature of information processing in autism should involve explaining both disordered processing as well as intact or superior abilities. Two theories which have sought to explain these patterns are the Weak Central Coherence hypothesis (Frith, 1989) and the Enhanced Perceptual Processing account (Mottron et al., 2006). Both models suggest that the default information processing in typical individuals is global, and that in individuals with autism it is local or detail-oriented. While the default local processing in autism may underlie their difficulties with higher cognitive functions, it may be an advantage in low level visuospatial tasks.  The latter is especially the case in visual search tasks where ignoring the global patterns makes it easier to find embedded targets. While the advantage in local level processing is well documented in autism (Happé & Frith, 2006), less is known about the nature of the neural circuitry underpinning this phenomenon.

Objectives: The primary aim of this study was to investigate the neural mechanisms involved in processing global versus local aspects of visual information in high-functioning children with autism.

Methods: Four high-functioning children (age range: 10-15 years) with autism and two typical control participants took part in this fMRI study (data collection is in progress). The stimuli consist of larger geometric shapes made of smaller ones. In the global task, participants are asked to identify the bigger picture whereas in the local task, they are asked to identify the parts that make up the bigger picture. The stimuli were presented in an event-related format. The fMRI data collected from the Siemens 3.0T Allegra scanner at the UAB Civitan International Research Center was analyzed using SPM8.

Results: The results indicate that while the control participants activated more in local processing task, the participants with autism showed more activation in global processing. More The control participants showed greater activation in the posterior parietal regions in the local task relative to the global task. Participants with autism, on the other hand, showed greater levels of activation in posterior parietal, in middle occipital, and in the dorsolateral prefrontal cortex in the global task. The results reported here are preliminary at this point, and reveals just a trend.

Conclusions: Greater activation in autism in frontal and occipital regions in global processing might indicate their relative difficulty in seeing the global pattern. Whereas, the increase in activation in parietal regions in control participants while processing local detail may suggest their increased effort to spot the local details in the geometric figures. Overall, the relative difficulty faced by controls and autistics may be different for different conditions since the default information processing style in each of these groups is different.