Quantitative estimation of changes in synchronization of the neuron firing in a frog’s cochlear nucleus with the sound signal envelope during long-term adaptation

Many of the second-order neurons located in the cochlear nucleus of the frog exhibited an increase in the synchronization of firing with the envelope of an amplitude-modulated signal in the course of long-term adaptation. For 80 neurons of the cochlear nucleus, the dependences of the synchronization coefficient and the phase of response on time (usually, within an interval of up to 36 s) were subjected to linear regression analysis. The slope of the regression lines for the synchronization coefficient was positive in most cases, and, for approximately half of the neurons, this dependence was reliable. The effect was observed for different modulation depths, different carrier levels, and different modulation frequencies. The phase of response tended to increase during long-term adaptation, but no definite correlation was observed between the temporal variations of the synchronization coefficient and the phase of response.