Inhibition of return: Neural basis and function

A goal of neuropsychology is to connect cognitive functions with underlying neural systems. Posner (1984; in press) has proposed a framework for doing so in which elementary mental operations in cognitive models are expressed in terms of component facilitations and inhibitions in the performance of normal persons. Studies of brain-injured patients are used to link these components to underlying neural systems. In the area of spatial attention one such component is the tendency to inhibit orienting towards visual locations which have been previously attended (inhibition of return). Here we report studies in patients and normals which demonstrate the relationship of this component to neural systems which generate saccades. The first experiment showed that midbrain lesions impairing saccade generation produced a concurrent loss of the inhibition of return, whereas cortical components shown to impair facilitatory components did not. The second and third experiments show that the inhibition of return is associated with a bias in eye movements against returning to a previously inhibited location and indicate that inhibition of return occurs even when the eyes are moved to an unchanging visual target. The deficits found in patients and the conditions under which the inhibition is found in normals suggest that inhibition of return may function to favour foveation of information at new locations.