SYNAPTIC MECHANISMS OF EXCITATION AND INHIBITION IN THE CENTRAL AUDITORY PATHWAY

Abstract

Transmembrane recordings were obtained from neurons of the inferior colliculus and medial geniculate body of the cat. Acoustic stimuli elicited EPSP''s, IPSP''s (which may be "active" inhibitory potentials), and combinations of the two. Large spikes were obtained, but stable recordings more commonly showed small (3-20 mV) spikes. Binaural interaction of the PSP"s and their precise temporal relationships have been demonstrated. Both inhibitory and excitatory PSP"s are a function of the tonal frequency and the intensity of stimuli. In response to a steady tonal stimulus, a unit can respond with either a long lasting hyperpolarization or depolarization of the membrane. These membrane changes continue for many seconds after the stimulus is stopped. Interval histograms for spike firing in response to different tonal frequencies have been obtained.