Intramodal and interaural specificity of the human slow auditory evoked potential

Parameters of slow auditory evoked potentials (SAEPs) recorded during monotonic monaural stimulation and a programmed change in the frequency of successive tonal stimuli were compared. In one variant of polytonic stimulation, besides the frequency, the side of stimulation also was changed (alternation). During polytonic stimulation the amplitude of the SAEPs was greater than during monotonic. Maximal amplitudes were found during alternating polytonic stimulation. A decrease in the variability of amplitude of the SAEPs and an increase in their peak latencies were observed during polytonic stimulation. It is concluded that SAEPs are characterized by intramodal and interaural specificity. The tonotopic and bilaterally symmetrical organizations of the system of SAEP generation can be demonstrated more satisfactorily at low sound intensities. Data indicating that neuron populations of the system of SAEP generation, perceiving tonal stimuli which differ very little from each other "overlap" to a greater degree than populations perceiving more different sounds, are given, The data on intramodal and interaural specificity of the SAEP are discussed from the standpoint of its extralemniscal origin.State Postgraduate Medical Institute, Tbilisi. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 460–468, September–October, 1977.