Intact spatial updating during locomotion after right posterior parietal lesions

One function of the posterior parietal cortex (PPC) is to monitor and integ rate sensory signals relating to the current pointing direction of the eyes . We investigated the possibility that the human PPC also contributes to sp atial updating juring larger-scale behaviors. Two groups of patients with b rain injuries either including or excluding the right hemisphere PPC and a group of healthy subjects performed a visually-directed walking task, in wh ich the subject views a target and then attempts to walk to it without visi on. All groups walked without vision accurately and precisely to remembered targets up to 6 m away; the patient groups also performed similarly to the healthy controls when indicating egocentric distances using non-motoric re sponses. These results indicate that the right PPC is not critically involv ed in monitoring and integrating non-visual self-motion signals, at least a long linear paths. In addition, visual perception of egocentric distance in multi-cue environments is immune to injury of a variety of brain areas. (C ) 2000 Elsevier Science Ltd. All rights reserved.