The functional organization of the auditory pathways

Abstract The search for a mechanism in the auditory system which sorts individual discriminable stimuli to unique sites has proved fruitless. The proportion of the system activated by any stimulus is so large that there is considerable overlap, and the appropriate response is dependent upon the activation of a certain pattern of fibres rather than a certain unique set of fibres. Simple features such as stimulus frequency, intensity, and relative time of arrival at the two ears seem to be adequately encoded in this way at the brainstem level. More complex features, such as the direction, and rate of change of stimulus frequency and intensity, and the position of a sound source in space, appear to be extracted only at the cortical level. There is an elaborate system of descending fibres, terminating in the brainstem auditory nuclei, which serve to control the “throughput” of sensory messages from the periphery.