Representation of visual space in area 7a neurons using the center of mass equation.

The firing rate of neurons in parietal area 7a of the behaving Rhesus monkey with its head fixed incorporates both visual and eye position information. This neural tuning is not in an ego-centered coordinate space. This physiological result was unexpected as behavioral deficits following parietal damage in human and monkey subjects suggested the existence of egocentric representations. A formulation to extract a world-centered system from area 7a neurons is presented that depends on the linearity of the eye position signal and the similarity of the equation describing the tuning of these neurons to the center of mass equation. This formulation permits the computation of the location of objects in world coordinates using either serial analysis of a single neuron's activity or parallel processing of a collection of neurons. Experimental predictions are made for the relationship between different parameters of angle of gaze neurons.