[Intramodal and interaural specificity of the human slow auditory evoked potential]

Parameters of slow auditory evoked potentials (SAEPs) evoked by monotonal monaural stimuli were compared with those evoked by a series of tone stimuli of different frequencies. In one version of polytonal stimulation the side of sound application was alternately varied. In the case of polytonal stimulation the amplitude of SAEPs was consistently greater than that in the case of monotonal stimulation. The maximal amplitudes were obtained during alternating polytonal stimulation. In the case of polytonal stimulation, together with the amplitude increase, a regular decrease in its variability was noticed. SAEPs recorded during polytonal stimulation were also characterized by greater peak-latency values. It is concluded that SAEPs possess intramodal and interaural specific properties. It is proved that the tonotopic and bilaterally symmetric organization of SAEP generating system is better manifested at lower sound intensities. The data demonstrate that neuron populations of the SAEP generating system which perceive slightly different sound stimuli overlap each other more than those which perceive more different sounds. The data on intramodal and interaural specificity of SAEP are discussed from the point of view of extralemniscal origin of this potential.