Categorical and coordinate spatial relations: fMRI evidence for hemispheric specialization

FUNCTIONAL magnetic resonance imaging (fMRI) was applied to determine the i nvolvement of the angular gyri in the processing of categorical and coordin ate spatial relations. In a categorical task, subjects were asked to judge whether a dot was presented above or below a horizontal line. In a coordina te task, they were asked to judge whether or not the distance between the d ot and the bar was within a reference distance. Results showed stronger act ivation of the left than of the right angular gyrus in the categorical task , and stronger activation, initially, of the right than of the left angular gyrus in the coordinate task. In addition, in the latter task, the involve ment of the right angular gyrus decreased with practice while that of the l eft angular gyrus increased. These results are interpreted in terms of the development of new categorical representations with practice in the coordin ate task. (C) 1999 Lippincott Williams & Wilkins.