Peripheral auditory processing, the precedence effect and responses of single units in the inferior colliculus

The purpose of this paper is to illustrate how interactions occurring within the auditory periphery are relevant to the interpretation of neurophysiological data obtained in recent studies seeking to find physiological correlates of ‘the precedence effect’. Similar information was presented orally at the recent International Symposium on the Central Auditory System held in Salamanca, Spain. The physiological data of interest are responses from single neural units in the inferior colliculus recorded following stimulation by successive pairs of binaural clicks. We show how peripheral, monaural, within-filter interactions of such successive clicks can produce internal values of interaural temporal differences (ITDs) and interaural intensitive differences (IIDs) that can differ greatly from those present in the external stimulus. These interactions can produce unintended internal ITDs and IIDs that are well ‘outside the tuning range’ of the single unit being studied. When this occurs, the responses of the single units to the pairs of clicks would be expected to diminish. We also discuss how hair cell-related adaptation and compression can also lead to diminished responses. It is suggested that effects resulting from peripheral interactions should be taken into account or evaluated quantitatively before other factors, including central inhibition, are invoked.