Intention-related activity in the posterior parietal cortex: a review

Over the last few years it is becoming increasingly apparent that an important role of the posterior parietal cortex is to process sensory information for the purpose of planning actions. We review studies showing that a large component of neural activity in area LIP is related to planning saccades and activity in a nearby parietal reach region (PRR) to reaches. This intention related activity dominates the delay period in delayed movement tasks, and also comprises a substantial component of the transient response. These findings, along with additional anatomical and physiological evidence, lends support to the idea that different cortical areas within the PPC represent plans for different actions. We also found strong modulation of activity when movement plans were changed without changes in the locus of attention. This result suggests that PPC, which has been postulated to play a role in shifting attention, may also play a role in changing movement intentions. Sensory related activity was also present in these tasks and may be related to the stimulus or to attention. These experiments show that there are intention and sensory related activities in the PPC consistent with its proposed role in sensory-motor transformations. These studies also show that care must be taken to measure intention-related signals and not assume that all task dependent modulation in the PPC reflects attention. (C) 2000 Elsevier Science Ltd. All rights reserved.