RESPONSE PROPERTIES OF CORTICOTECTAL AND CORTICOSTRIATAL NEURONS IN THE POSTERIOR LATERAL SUPRASYLVIAN CORTEX OF THE CAT

Lateral suprasylvian cortex (LS) is an important source of visual proj ections to both the striatum and superior colliculus. Although these t wo LS efferent systems are likely to be involved in different aspects of visual processing, little is known about their functional propertie s. In the present experiments, 86 neurons in halothane-anesthetized, p aralyzed cats were recorded along the posterior aspects of the medial and lateral banks of LS (PMLS and PLLS). Neurons were selected for ana lysis on the basis of antidromic activation from electrodes chronicall y implanted in the superior colliculus and caudate nucleus. The segreg ated nature of corticostriatal and corticotectal neurons was apparent; in no instance could a neuron be antidromically activated from both t he superior colliculus and the caudate nucleus. Many common features w ere revealed between corticotectal and corticostriatal neurons; the ma jority of neurons in both populations were binocular and contralateral ly dominant, showed similar responses to stationary flashed light, and expressed within-field spatial summation and surround inhibition. How ever, a number of information-processing features distinguished betwee n corticotectal and corticostriatal neurons; the former were generally tuned to lower velocities than were the latter, and, for a given ecce ntricity in visual space, corticotectal neurons had smaller receptive fields than did corticostriatal neurons. Moreover, most corticotectal neurons displayed a marked preference for movements toward temporal vi sual space, whereas corticostriatal neurons revealed no specialization for a particular direction of movement. In addition, whereas corticot ectal neurons were selective for receding stimuli, corticostriatal neu rons were selective for approaching stimuli. The presence of these two corticofugal pathways is discussed in relation to their presumptive f unctional roles in the facilitation of attentive and orientation behav iors.