Differences In Global and Local Level Information Processing In Autism: An fMRI Investigation

Background:  

The theory of weak central coherence (WCC) proposes that people with autism have compromised perception of global, holistic information, whereas people without autism generally show a strong bias for holistic perception¹. As a consequence, people with autism may be relatively good at tasks where attention to local detail is advantageous.  This theory may explain why people with autism have difficulty with tasks involving global perception, including recognition of faces and understanding words in context, while at the same time exhibiting relatively enhanced or preserved performance of tasks that involve local detail processing such as the Block Design and Embedded Figures tasks³.  There is little functional neuroimaging evidence, however, that persons with autism subjects have impaired global processing.  Previous fMRI studies have focused on local detail processing but not global processing differences in autism.^2,3,4

Objectives:  

Our main objective was to conduct an fMRI study of both global and local attention in persons with autism. 

Methods:  

Seventeen adults with autism spectrum disorders (Autistic Disorder and Asperger’s Syndrome) and 16 healthy control subjects participated in an fMRI experiment. Subjects were studied using a 3T whole body magnet while performing a target detection task using hierarchical abstract shapes. Attention was focused on either global shape or local shape target detection in a blocked fashion. fMRI data were analyzed using SPM8. 

Results:  

Results were corrected for multiple comparison using alphasim height and extent thresholds and random field theory. The pattern of activation for both groups and both attention conditions (local and global) was similar and included activation of attention and cognitive control networks (bilateral parietal BA7, frontal operculum, dorsolateral prefrontal cortex and pre-supplemental motor area/cingulate gyrus), as well as ventral visual stream regions including the lateral occipital cortex. In both attention conditions, the autism group exhibited significantly greater activation of the right lateral occipital visual region than controls. Relative to controls, the autism group showed greater activation of medial prefrontal cortex than controls in the global condition compared to the local condition and greater activation than controls in right prefrontal cortex for local compared to global attention. 

Conclusions:  

These findings may suggest greater difficulty in maintenance of attentional set and cognitive control as well as greater early visual processing of both global and local information in autism.

References:

1. Frith, U. and F. Happe (1994). "Autism: beyond "theory of mind"." Cognition 50(1-3): 115-32.

2. Lee, P. S., J. Foss-Feig, et al. (2007). "Atypical neural substrates of Embedded Figures Task performance in children with Autism Spectrum Disorder." Neuroimage 38(1): 184-93.

3. Manjaly, Z. M., N. Bruning, et al. (2007). "Neurophysiological correlates of relatively enhanced local visual search in autistic adolescents." Neuroimage 35(1): 283-91.

4. Ring, H. A., S. Baron-Cohen, et al. (1999). "Cerebral correlates of preserved cognitive skills in autism: a functional MRI study of embedded figures task performance." Brain 122 (Pt 7): 1305-15.