Pitch and Cochlear Nerve Fibre Temporal Discharge Patterns

Abstract

Controversy still exists concerning the role played by the temporal discharge patterns of cochlear nerve fibres in determining the pitch assigned to complex stimuli (see Evans, 1978 for review). Recently, attention has been focussed on a stimulus, similar to one originally used by Seebeck, consisting of a pulse train having alternate intervals of 4.7 and 5.3 ms (Whitfield, 1979, 1980; Moore, 1980). This stimulus, when heard unfiltered has an ambiguous pitch of 100 or 200 Hz. In contrast, Whitfield (1979, 1980) reported intervals corresponding to the 4.7 and 5.3 ms intervals in the stimulus to predominate in the interspike interval histograms (ISIH) of cochlear nerve fibres having characteristic frequencies (CFs) from 0.55 to 2 kHz, in the guinea pig. He consequently raised the questions why the pitches corresponding to these intervals were not heard, and conversely why the 200 Hz pitch heard appeared to have no corresponding interval in the neural discharge patterns. In response, Moore (1980) has argued that neural intervals corresponding to the pitches heard should be present in the discharge patterns of cochlear fibres of CFs corresponding to the dominant region for the pitch heard, usually some 3–5 times the frequency matching the pitch.