[Cross-correlation analysis of auditory neuron activity in response to acoustic clicks]

Cross correlation function relating the output spike train and the input puassoneous click trains were obtained for 213 single units located in the auditory midbrain center of the frog (Rana ridibunda). Five types of responses were found: type 1 (29 units) was due to polysynaptic unimodal excitation, type II (73 units) resulted from excitation followed by inhibition, type III (26 units) resulted from inhibition followed by excitation. In the IVth type (36 units) the excitation was preceded and followed by inhibition. The neurons of the Vth type had bimodal or trimodal correlation functions. The cross correlation functions allow to estimate the temporal shape of postsynaptic excitability changes and to reveal the inhibitory stimulus effects even for the units escaping spontaneous impulsation.