Patterns of responses of cortical cells to binaural stimulation

The relationship between stimulus intensity and response latency implies that the relative time of arrival of input to binaurally sensitive loci can vary over a range significantly longer than the interaural delays resulting from the travel time of sound between the ears. To investigate the effect of such potentially long inter-arrival time intervals, responses of binaurally sensitive neurons in auditory cortex of cats were examined over relatively long interaural delays. Two kinds of interaural delay functions were observed. One kind involved a sharp transition to a reduced response rate over a narrow range of interaural delays, while the other involved a gradual reduction of response rate over a relatively prolonged range of interaural delays. The amount of suppression was found to be a sensitive function of both interaural delay and the relative intensity of the stimuli delivered to the two ears. The pattern of suppression across a binaural response was stationary with respect to the excitatory contralateral stimulus over wide ranges of interaural delay. In addition, certain characteristics of a group of cells generally responsive only to binaural stimulation are described. A model is proposed which accounts for the observed stationarity of the response suppression.