HEAD POSITION SIGNALS USED BY PARIETAL NEURONS TO ENCODE LOCATIONS OFVISUAL-STIMULI

THE mechanism for object location in the environment, and the percepti on of the external world as stable when eyes, head and body are moved, have long been thought to be centred on the posterior parietal cortex (1-8). However, head position signals, and their integration with visu al and eye position signals to form a representation of space referenc ed to the body, have never been examined in any area of the cortex. He re we show that the visual and saccadic activities of parietal neurons are strongly affected by head position. The eye and head position eff ects are equivalent for individual neurons, indicating that the modula tion is a function of gaze direction, regardless of whether the eyes o r head are used to direct gaze. These data are consistent with the ide a that the posterior parietal cortex contains a distributed representa tion of space in body-centred coordinates.