Eye-centered remapping of remembered visual space in human parietal cortex

Abstract

Neurophysiological evidence suggests that the monkey posterior parietal cortex represents and updates visual space in eye-centered coordinates (Duhamel et al. Science 1992; Batista et al. Science 1999). Using event-related fMRI, we investigated whether the human posterior parietal cortex employs a similar mechanism to internally update spatial representations for both eye and arm movements. We first identified a bilateral parietal region with activity related to the remembered location of a visual goal in contralateral space. We then tracked this activity while subjects viewed two sequentially flashed “goal” and “fixation” targets at randomized horizontal locations, shifted their eyes toward the fixation target, and then either looked or pointed toward the remembered location of the goal. On any given trial the goal target could be to the left or right of the fixation target. The fMRI signal was always related to the horizontal location of the remembered goal relative to gaze. When eye movements reversed the remembered horizontal goal location relative to the gaze fixation point, a dynamic shift in cortical activity from one hemisphere to the other occurred. We conclude that in the human posterior parietal cortex, spatial goals for eye and arm movements are stored and remapped in eye-centered coordinates.