Imagined transformations of bodies: an fMRI investigation

A number of spatial reasoning problems can be served by performing an imagi ned transformation of one's egocentric perspective. A series of experiments were carried out to characterize this process behaviorally and in terms of its brain basis, using functional magnetic resonance imaging (fMRI). In a task contrast designed to isolate egocentric perspective transformations, p articipants were slower to make left-right judgments about a human figure f rom the figure's perspective than from their own. This transformation led t o increased cortical activity around the left parietal-temporal-occipital j unction, as well as in other areas including left frontal cortex. In a seco nd task contrast comparing judgments about inverted figures to judgments ab out upright figures (always from the figure's perspective), participants we re slower to make left-right judgments about inverted figures than upright ones. This transformation led to activation in posterior areas near those a ctive in the first experiment, but weaker in the left hemisphere and strong er in the right, and also to substantial left frontal activation. Together, the data support the specialization of areas near the parietal-temporal-oc cipital junction for egocentric perspective transformations. These results are also suggestive of a dissociation between egocentric perspective transf ormations and object-based spatial transformations such as mental rotation. (C) 1999 Elsevier Science Ltd. All rights reserved.