In order to direct a movement towards a visual stimulus, visual spatial information must be combined with postural information. For example, directing gaze (eye plus head) towards a visible target requires the combination of retinal image location with eye and head position to determine the location of the target relative to the body. Similarly, world-referenced postural information is required to determine where something lies in the world. Posterior parietal neurons recorded in monkeys combine visual information with eye and head position. A population of such cells could make up a distributed representation of target location in an extraretinal frame of reference. However, previous studies have not distinguished between world-referenced and body-referenced signals. Here we report that modulations of visual signals (gain fields) in two adjacent cortical fields, LIP and 7a, are referenced to the body and to the world, respectively. This segregation of spatial information is consistent with a streaming of information, with one path carrying body-referenced information for the control of gaze, and the other carrying world-referenced information for navigation and other tasks that require an absolute frame of reference.

The mechanism for object location in the environment, and the perception 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. However, head position signals, and their integration with visual and eye position signals to form a representation of space referenced to the body, have never been examined in any area of the cortex. Here we show that the visual and saccadic activities of parietal neurons are strongly affected by head position. The eye and head position effects are equivalent for individual neurons, indicating that the modulation is a function of gaze direction, regardless of whether the eyes or head are used to direct gaze. These data are consistent with the idea that the posterior parietal cortex contains a distributed representation of space in body-centred coordinates.