Functional Anatomy of Compensatory Processing in Autistic Attention: Complementary Roles of Selection and Suppression


Matthew Belmonte and Deborah Yurgelun-Todd


November 1-2, 2002
Orlando, Florida

ABSTRACT

Despite a deficit in rapid re-allocation of attention, and absence of normal physiological indices of attentional selection, people with autism display intact and even superior performance on many attentional tasks. When attentional selection is impaired developmentally, compensatory cognitive strategies may be brought into play in order to achieve functional behavioural performance. On the basis of an fMRI study of visual spatial attention, we previously reported that in autism, generalised arousal substitutes for early selective attention. In an extension of this work, we have localised in intraparietal sulcus a process of suppression of irrelevant stimuli which may compensate for impaired selective processing. Subjects viewed coloured squares flashed at 9 Hz in the left and right upper quadrants. A red square in the attended location cued not only an overt behavioural response but also a covert shift of attention to the opposite hemifield. In echo-planar images acquired at 1.5T, effects of leftward and rightward directed attention were compared using a permutation test within regions of interest defined a priori on the basis of individual functional maps. In comparison with a group of normal subjects matched for age and sex, a group of 6 subjects with autism showed less attention-related activity in ventral occipital cortex contralateral to the attended hemifield (p < 0.03), and greater attention-related activity in intraparietal sulcus contralateral to the suppressed hemifield (p < 0.04). In addition to these findings, we will report preliminary measurements on frontal regions.
 Supported by the National Alliance for Autism Research.