Input–output functions of cochlear whole-nerve action potentials: Interpretation in terms of one population of neurons

Abstract

It is commonly assumed that the two‐segmented input–output functions of the whole‐nerve action potential are a result of the activity of two sets of primary fibers: a low‐ and a high‐sensitivity group. While anatomical studies show the existence of two populations of fibers, there are no clear‐cut electrophysiological signs of two distinct populations responding with different thresholds. In light of this physiological result, it is desirable to construct a scheme for the growth of the whole‐nerve action potential that involves only one group of fibers. This can be done in a qualitative fashion by considering the pattern of single‐unit tuning curves and assessing the contribution of populations of units to the compound response. Thus the slowly growing low‐level segment of the input–output function is identified with the sharp tip region of the tuning curves of the responding units, while the high‐level, rapidly growing, segment is associated with the recruitment of higher‐frequency units that respond on the tail segment of their tuning curves. Thus the low and high parts of the input–output functions are interpreted in terms of the excitation of narrow and wide segments of the cochlear receptor. Masking experiments that support the scheme are described. Subject Classification: [43]65.35, [43]65.42, [43]65.59, [43]65.40.