A field potential study of inhibition in the cat superior olivary complex

Abstract

The medial superior olive (MSO) is an important nucleus in the coding of sound localization (Galambos et al, 1959), and it has been shown that inter-aural time delays can result in the suppression of the firing of cells in this nucleus (Rupert et al, 1966). Therefore, it is possible that an interplay between excitation and inhibition is responsible for the coding of sound localization. Consequently, the present study was undertaken to examine the inhibitory mechanisms in the MSO.

The inhibitory mechanisms in the MSO in this study have been studied largely by measuring the changes in the amplitude of the field potential of a test stimulus, when presented at various intervals after a conditioning stimulus. The hypotheses that have been tested have been developed from the initial studies on inhibition of spinal motoneurons (Brock et al, 1951; Frank and Fuortes, 1957; Frank, 1959). These have shown that inhibition may be presynaptic or postsynaptic. In the present study, it was considered that observations on the duration of the suppression of field potentials could show a difference between occlusion and inhibition, as occlusion, which is due to a refractory state in nerve tissue, has a shorter duration than inhibition. Inhibition in the medial geniculate body of the cat has also been studied by recording field potential changed (Aitkin and Dunlop, 1969).