Classification of frequency response areas in the inferior colliculus reveals continua not discrete classes

Palmer, A.R., Shackleton, T.M., Sumner, C.J. ORCID: 0000-0002-2573-7418, Zobay, O. and Rees, A., 2013. Classification of frequency response areas in the inferior colliculus reveals continua not discrete classes. The Journal of Physiology, 591 (16), pp. 4003-4025. ISSN 0022-3751

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A differential response to sound frequency is a fundamental property of auditory neurons. Frequency analysis in the cochlea gives rise to V-shaped tuning functions in auditory nerve fibres, but by the level of the inferior colliculus (IC), the midbrain nucleus of the auditory pathway, neuronal receptive fields display diverse shapes that reflect the interplay of excitation and inhibition. The origin and nature of these frequency receptive field types is still open to question. One proposed hypothesis is that the frequency response class of any given neuron in the IC is predominantly inherited from one of three major afferent pathways projecting to the IC, giving rise to three distinct receptive field classes. Here, we applied subjective classification, principal component analysis, cluster analysis, and other objective statistical measures, to a large population (2826) of frequency response areas from single neurons recorded in the IC of the anaesthetised guinea pig. Subjectively, we recognised seven frequency response classes (V-shaped, non-monotonic Vs, narrow, closed, tilt down, tilt up and double-peaked), that were represented at all frequencies. We could identify similar classes using our objective classification tools. Importantly, however, many neurons exhibited properties intermediate between these classes, and none of the objective methods used here showed evidence of discrete response classes. Thus receptive field shapes in the IC form continua rather than discrete classes, a finding consistent with the integration of afferent inputs in the generation of frequency response areas. The frequency disposition of inhibition in the response areas of some neurons suggests that across-frequency inputs originating at or below the level of the IC are involved in their generation.

Item Type: Journal article
Publication Title: The Journal of Physiology
Creators: Palmer, A.R., Shackleton, T.M., Sumner, C.J., Zobay, O. and Rees, A.
Publisher: John Wiley & Sons Ltd. on behalf of The Physiological Society
Date: 14 August 2013
Volume: 591
Number: 16
ISSN: 0022-3751
Rights: © 2013 The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Divisions: Schools > School of Social Sciences
Record created by: Jill Tomkinson
Date Added: 04 Mar 2019 14:36
Last Modified: 04 Mar 2019 14:36

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