Cortical underconnectivity coupled with preserved visuospatial cognition in autism: Evidence from an fMRI study of an embedded figures task

Abstract

Individuals with high-functioning autism sometimes exhibit intact or superior performance on visuospatial tasks, in contrast to impaired functioning in other domains such as language comprehension, executive tasks, and social functions. The goal of the current study was to investigate the neural bases of preserved visuospatial processing in high-functioning autism from the perspective of the cortical underconnectivity theory. We used a combination of behavioral, functional magnetic resonance imaging, functional connectivity, and corpus callosum morphometric methodological tools. Thirteen participants with high-functioning autism and 13 controls (age-, IQ-, and gender-matched) were scanned while performing an Embedded Figures Task. Despite the ability of the autism group to attain behavioral performance comparable to the control group, the brain imaging results revealed several group differences consistent with the cortical underconnectivity account of autism. First, relative to controls, the autism group showed less activation in the left dorsolateral prefrontal and inferior parietal areas and more activation in visuospatial (bilateral superior parietal extending to inferior parietal and right occipital) areas. Second, the autism group demonstrated lower functional connectivity between higher-order working memory/executive areas and visuospatial regions (between frontal and parietal-occipital). Third, the size of the corpus callosum (an index of anatomical connectivity) was positively correlated with frontal-posterior (parietal and occipital) functional connectivity in the autism group. Thus, even in the visuospatial domain, where preserved performance among people with autism is observed, the neuroimaging signatures of cortical underconnectivity persist.

FIGURE 1

Examples of the EFT stimuli used in the current study. Answer to (A): Purple and green surfaces at the back lower right. Answer to (B): A catch-trial.

FIGURE 2

Between-group contrasts of activation for EFT-Fixation. Group difference showing areas where the autism group had more activation than controls (A); Group difference showing areas where the participants with autism had less activation than the control group (B).

FIGURE 3

Functional connectivity interaction between group (participants with autism and control participants) and connection type (Frontal-Posterior ROI pairs versus Other pairs of ROIs), along with individual participants’ functional connectivity data.

FIGURE 4

Correlation between the midsagittal area of the corpus callosum and the mean functional connectivity between frontal-posterior areas for autism (A) and controls (B).