Spontaneous Activity of Auditory Afferent Neurones in the Spiral Ganglion of the Pigeon

Abstract

In the avian (Manley, 1979; Manley and Gleich, 1984; Manley et al., 1985; Temchin, 1988) and reptilian (Crawford and Fettiplace, 1980; Eatock et aI., 1981) auditory nerves there exists a population of afferent fibres which exhibit quasiperiodic spontaneous activity. The interval histogram of such activity shows decaying maxima, separated at approximately equal intervals, named the preferred interval by Manley (1979). These histograms contrast with those reported for other species (e.g. Kiang, 1965; Walsh et al., 1972; Robertson and Manley, 1974), and with the balance of histograms from other fibres in birds and reptiles, where after an absolute refractory period the interval histogram decays exponentially from it’s modal value, as if generated by a truncated, homogeneous Poisson process. However, for quasiperiodic spontaneous activity both the modal interval and the preferred interval are related to the characteristic frequency (CF) of the neurone. Earlier reports (Manley, 1979; Crawford and Fettiplace, 1980; Eatock et al., 1981), as well as the one by Temchin(1988), report that the modal and preferred intervals are approximately equal to the CF-period, whereas the more recent papers from Manley and coworkers (Manley and Gleich, 1984; Manley et al., 1985) maintain that these intervals are on average 15% longer than the CF-period. In these papers Manley estimated the preferred interval as the weighted average of the intervals of the second and higher maxima of the interval histogram, whereas Temchin(1988) calculated it from the number of minima in a specified time frame of the autocorrelation histogram.