Auditory units in the medulla of the marsh frog with unusual patterns of spontaneous activity

Abstract

Statistical properties of spontaneous firing were studied in 79 single auditory units located in the dorsal medullar (cochlear) nucleus of unanaesthetized curarized marsh frogs (Rana ridibunda). The great majority of these units showed irregular spontaneous activity with mean rates in the range 1–30 spikes · s−1. In 53% of the cells the auto-renewal functions of the spontaneous activity monotonically rose to an asymptotic value, but 41% of the cells produced auto-renewal functions which showed a pronounced peak after a dead-time period. Five low-frequency auditory neurons revealed periodic firing in the absence of controlled stimuli. The preferred period did not correspond to the unit's best frequency but demonstrated a modest correlation with the best modulation frequency of the unit's response to amplitude-modulated tones and with the duration of the after-onset dip in peri-stimulus time histograms.