The Journal of Neuroscience, October 15, 1999, 19(20):9039-9053
Vector Averaging Occurs Downstream from Learning in Smooth
Pursuit Eye Movements of Monkeys
Maninder
Kahlon and
Stephen G.
Lisberger
Howard Hughes Medical Institute, Department of Physiology,
Neuroscience Graduate Program, and W. M. Keck Foundation Center
for Integrative Neuroscience, University of California, San Francisco,
California 94143
How are sensory-motor transformations organized in a cortical motor
system? In general, sensory information is transformed through a
variety of signal processing operations in the context of distinct
coordinate frameworks. We studied the interaction of two distinct
operations in pursuit eye movements, learning and vector-averaging, to
gain insight into their underlying coordinate frameworks and their
sequence in sensory-motor processing. Learning was induced in the
initiation of pursuit eye movements by targets that moved initially at
one speed for 100 msec and then increased or decreased to a sustained
final speed. Vector averaging was studied by comparing the initial eye
acceleration evoked by the simultaneous motion of two targets with that
evoked by each target singly. Learning caused specific effects on the
direction of the vector-averaged responses to two-target stimuli that
included one target moving in the direction used to induce learning.
Learned increases or decreases in eye acceleration caused the direction of the responses to two-targets to rotate toward or away from the
learning direction. Learning also caused nonspecific changes in the
responses to two-target stimuli. After any learning protocol, two-target responses usually became smaller, and their directions rotated away from the axis of the target motion used for learning. Quantitative analysis showed that the specific effects of learning were
predicted most closely by a model in which vector averaging occurs
downstream from the site(s) of learning. We suggest that the pursuit
system creates parallel commands for potential movements to each of the
targets in two-target stimuli, and that learning occurs in the
coordinates of the potential movements.
Key words:
oculomotor system; sensory-motor transformation; coordinate system; population code; visual-motor processing; learning
Copyright © 1999 Society for Neuroscience 0270-6474/99/19209039-15$05.00/0
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