EYE POSITION TUNING IN PRIMATE AUDITORY CORTEX.  U.Werner-Reiss*;
K.A.Kelly; A.M.Underhill; J.M.Groh Psychol. and Brain Sci., Dartmouth
College, Hanover, NH, USA

The location of a sound source can be deduced from differences in
sound arrival time and pressure level across the two ears. These cues
yield a head-centered frame of reference for encoding sound
location. However, we have previously reported that both eye position
and sound location modulate the responses of some neurons in two areas
of the primate auditory pathway, the inferior colliculus (Neuron,
29:509) and auditory cortex (Soc. Neurosci. Abst., 26:1977). This
modulation by eye position results in a representation for sound
location that is neither head- nor eye-centered.

In this study we explore the tuning for eye position in primate
auditory cortex. The monkey fixated visual stimuli at 9 possible
locations (24 degrees left to 24 degrees right) while noise bursts
were presented from 9 different speakers at the same horizontal
locations. Eye position modulated the auditory responses of more than
half of the neurons in auditory cortex. The influence of eye position
on the auditory responses was often complex and varied from cell to
cell. Across the population, cell responses frequently increased or
decreased symmetrically as the eyes moved to eccentric positions
(either ipsilateral or contralateral). This pattern suggests that the
eye position signal influencing the auditory response reflects
deviations of the eyes from straight ahead. Supported by: ONR,
Whitehall, McKnight, Sloan, John Merck, and NIH 17778-19 grants to
JMG.