Gain Adaptation of Eye and Head Movement Components of Simian Gaze Shifts.
James O. Phillips, Albert F. Fuchs, Leo Ling, Yoshiki Iwamoto, and Scott
Votaw.
Department of Physiology & Biophysics and Regional Primate Research Center,
University of Washington, Seattle, WA 98195.
APStracts 4:166N, 1997.
ABSTRACT
To investigate the site of gaze adaptation in primates, we reduced the gain of
large head-restrained gaze shifts made to 50 target steps by jumping the
target 40% backwards during a targeting saccade and then tested gain transfer
to the eye- and head-movement components of head-unrestrained gaze shifts.
After several hundred backstep trials, saccadic gain decreased by at least 10%
in 8/13 experiments, which were then selected for further study. The minimum
saccadic gain decrease in these 8 experiments was 12.8% (mean = 18.4%). Head-
unrestrained gaze shifts to ordinary 50 target steps experienced a gain
reduction of at least 9.3% (mean = 14.9), a mean gain transfer of 81%. Both
the eye and head components of the gaze shift also decreased. However, average
head movement gain decreased much more (22.1%) than eye movement gain (9.2%).
Also, peak head velocity generally decreased significantly (20%), but peak eye
velocity either increased or remained constant (average increase of 5.6%).
However, the adapted peak eye and head velocities were appropriate for the
adapted, smaller gaze amplitudes. Similar dissociations in eye and head
metrics occurred when head-unrestrained gaze shifts were adapted directly
(N=2). These results indicated that head-restrained saccadic gain adaptation
did not produce adaptation of eye movement alone. Nor did it produce a
proportional gain change in both eye and head movement. Rather, normal eye
and head amplitude and velocity relations for a given gaze amplitude were
preserved. Such a result could be explained most easily if head-restrained
adaptation were realized before the eye and head commands had been
individualized. Therefore, gaze adaptation is most likely to occur upstream of
the creation of separate eye and head movement commands.
Received 18 April 1997; accepted in final form 21 July 1997.
APS Manuscript Number J316-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 28 August 1997