%0 Journal Article
%T Perception and coding of high-frequency spectral notches: potential implications for sound localization
%A Ana Alves-Pinto
%A Alan R. Palmer
%A Enrique A. Lopez-Poveda
%J Frontiers in Neuroscience
%D 2014
%I Frontiers Media
%R 10.3389/fnins.2014.00112
%X The interaction of sound waves with the human pinna introduces high-frequency notches (5¨C10 kHz) in the stimulus spectrum that are thought to be useful for vertical sound localization. A common view is that these notches are encoded as rate profiles in the auditory nerve (AN). Here, we review previously published psychoacoustical evidence in humans and computer-model simulations of inner hair cell responses to noises with and without high-frequency spectral notches that dispute this view. We also present new recordings from guinea pig AN and ˇ°ideal observerˇ± analyses of these recordings that suggest that discrimination between noises with and without high-frequency spectral notches is probably based on the information carried in the temporal pattern of AN discharges. The exact nature of the neural code involved remains nevertheless uncertain: computer model simulations suggest that high-frequency spectral notches are encoded in spike timing patterns that may be operant in the 4¨C7 kHz frequency regime, while ˇ°ideal observerˇ± analysis of experimental neural responses suggest that an effective cue for high-frequency spectral discrimination may be based on sampling rates of spike arrivals of AN fibers using non-overlapping time binwidths of between 4 and 9 ms. Neural responses show that sensitivity to high-frequency notches is greatest for fibers with low and medium spontaneous rates than for fibers with high spontaneous rates. Based on this evidence, we conjecture that inter-subject variability at high-frequency spectral notch detection and, consequently, at vertical sound localization may partly reflect individual differences in the available number of functional medium- and low-spontaneous-rate fibers.
%K auditory nerve
%K rate profile
%K phase-locking
%K temporal profile
%K head-related transfer function
%K HRTF
%U http://www.frontiersin.org/Journal/10.3389/fnins.2014.00112/abstract