Multiple Parietal Representations of Space

Publisher Summary This chapter discusses multiple parietal representations of space. Posterior parietal cortex is divided into a number of separate areas. These parietal areas do not typically contain simple retinotopic maps and their borders cannot be defined with reference to ventral or horizontal meridian representations. Parietal areas have instead been initially identified on the basis of their connections with other cortical areas. Neurons in the lateral intraparietal (LIP) area are active in relation to both visual and oculomotor events. They discharge when a visual stimulus appears in the receptive field and, for about half the population, discharge again when a saccade to the location is executed cued by the stimulus. The failure to shift the LIP representation in conjunction with an attentional shift suggests that the function of remapping is to maintain an accurate alignment between the visual world and its internal representation. Visual responses of neurons in LIP are modulated both by overt movements of the eyes and by covert shifts of attention. Quite different purposes are served by sensitivity to intended eye movements and to attentional shifts. Response modulation by attentional state permits enhanced processing of images within the focus of attention.