Journal of Neurophysiology, Vol 67, Issue 6 1428-1436, Copyright © 1992 by APS
Response of auditory units in the barn owl's inferior colliculus to continuously varying interaural phase differences
A. Moiseff and T. Haresign
Department of Physiology and Neurobiology, University of Connecticut, Storrs 06269.
1. We studied the response of single units in the central nucleus of the
inferior colliculus (ICc) of the barn owl (Tyto alba) to continuously
varying interaural phase differences (IPDs) and static IPDs. Interaural
phase was varied in two ways: continuously, by delivering tones to each ear
that varied by a few hertz (binaural beat, Fig. 1), and discretely, by
delaying in fixed steps the phase of sound delivered to one ear relative to
the other (static phase). Static presentations were repeated at several
IPDs to characterize interaural phase sensitivity. 2. Units sensitive to
IPDs responded to the binaural beat stimulus over a broad range of delta
f(Fig. 4). We selected a 3-Hz delta f for most of our comparative
measurements on the basis of constraints imposed by our stimulus generation
system and because it allowed us to reduce the influence of responses to
stimulus onset and offset (Fig. 3A). 3. Characteristic interaural time or
phase sensitivity obtained by the use of the binaural beat stimulus were
comparable with those obtained by the use of the static technique (Fig. 5;
r2 = 0.93, Fig. 6). 4. The binaural beat stimulus facilitated the
measurement of characteristic delay (CD) and characteristic phase (CP) of
auditory units. We demonstrated that units in the owl's inferior colliculus
(IC) include those that are maximally excited by specific IPDs (CP = 0 or
1.0) as well as those that are maximally suppressed by specific IPDs (CP =
0.5; Figs. 7 and 8). 5. The selectivity of units sensitive to IPD or
interaural time difference (ITD) were weakly influenced by interaural
intensity difference (IID).(ABSTRACT TRUNCATED AT 250 WORDS)
