ACTIVE REPRESENTATION OF SHAPE AND SPATIAL LOCATION IN MAN

Neural activity during the delay period of spatial delayed response (D R) and delayed matching (DM) tasks was investigated by positron emissi on tomography A distributed cortical system was activated in each cond ition. The bilateral dorsolateral prefrontal cortex (DLPFC) was activa ted in the delay period of both tasks; activation was of higher signif icance on the right in the DR task and the left in the DM task, and ex tended to the anterolateral prefrontal cortex in the DM condition. Act ive representation of spatial location in the DR task was associated w ith co-activation of the medial and lateral parietal cortex and the ex trastriate visual cortex. Active representation of shape in the DM tas k was associated with co-activation of the medial and lateral parietal cortex and the inferior temporal cortex. Response-related activity wa s observed in both tasks. Activation of anterior cingulate, inferior f rontal, lateral premotor and rostral inferior parietal cortex was obse rved in the DR condition, a task characterized by preparation of a mov ement to a predetermined location. In contrast, preparation to move to an undetermined location in the DM task was associated with activatio n predominantly in rostral SMA.