The Journal of Neuroscience, February 15, 2002, 22(4):1468-1479
The Coding of Spatial Location by Single Units in the Lateral
Superior Olive of the Cat. II. The Determinants of Spatial Receptive
Fields in Azimuth
Daniel J.
Tollin and
Tom C. T.
Yin
Department of Physiology, University of Wisconsin-Madison, Madison,
Wisconsin 53706
The lateral superior olive (LSO) is one of the most peripheral
nuclei in the auditory pathway to receive inputs from both ears, and
its cells are sensitive to interaural level disparities (ILDs) when
stimulated by sounds presented over earphones. It has, accordingly,
long been hypothesized that the functional role of the LSO is to encode
a correlate of ILDs, one of the acoustical cues to the spatial location
of sound. In the companion paper, we used the virtual space (VS)
technique to present over earphones stimuli containing all the
acoustical cues to the location of broadband stimuli and measured the
spatial receptive fields (SRFs) in azimuth of single LSO cells. The
shapes of the SRFs were generally consistent with the ILD sensitivity
of the cells (Tollin and Yin, 2002), but because the only
variable under our control was azimuth, and not ILD directly, the
precise cues responsible for the SRFs could not be unambiguously
determined. Here, we test more directly the hypothesis that ILDs are
the primary determinants of the SRFs in azimuth of LSO cells by
digitally manipulating the head-related transfer functions used to
create the VS stimuli by independently varying (or holding constant) in
azimuth each of the primary localization cues in isolation while
holding constant (or varying) the others. Our results support the
classical view of the LSO that the form of the SRFs of the cells in
azimuth is determined primarily by the ILDs in a small band of
frequencies around the characteristic frequencies of the cells.
Key words:
lateral superior olive; head-related transfer function; sound localization; interaural level difference; interaural time
difference; cat
Copyright © 2002 Society for Neuroscience 0270-6474/02/2241468-12$05.00/0