Neural Foundations of Vision 
analyses of visual cortical function. We are also 
applying methods derived from statistical deci- 
sion theory to the question of the absolute effi- 
ciency of visual representations in the brain. 
In addition to its purely visual functions, the M 
stream provides signals that drive eye movements 
of pursuit, the slow, smooth eye movements with 
which primates stabilize on the retina the image 
of a moving visual target. In collaboration with 
Stephen Lisberger (University of California, San 
Francisco), we have studied several aspects of the 
relationship between visual and visuomotor pro- 
cesses. In a series of neurophysiological studies, 
we have explored the responses of MT neurons to 
the dynamic motion profiles used to characterize 
pursuit and have documented the suitability of 
the motion-related signals in these neurons for 
the task of initiating pursuit. In psychophysical 
work, we have begun to explore the kinds of vi- 
sual signals that pass into the oculomotor system 
by examining the relationship between the de- 
tectability of particular visual patterns and the 
pursuit eye movements they elicit. 
Our overall ambition for these studies is to 
"turn the sensory-motor corner" and relate the 
particulars of visual processing to the higher 
mechanisms that produce voluntary motor com- 
mands. To this end, we are developing computa- 
tional models designed to explain the signal 
transformations that take place at a series of stages 
between the initial registration of the visual 
image and the formulation of the final oculomo- 
tor command. 
To analyze development, in a project sup- 
ported by the National Eye Institute, we study the 
vision of monkeys reared either with an artificial 
strabismus (deviation of one eye) or anisometro- 
pia (difference in the refractive state of the two 
eyes) . Both of these manipulations lead to condi- 
tions resembling human amblyopia, a common 
visual deficit of central nervous system origin. In 
behavioral experiments, we learn how experi- 
mental amblyopia affects perceptually defined 
mechanisms that support visual sensitivity to 
form, contrast, and position. Neurophysiological 
studies in the same animals then reveal alter- 
ations in cortical neuron properties that seem to 
be related to the psychophysical ly measured vi- 
sual deficits. 
Using this strategy, we seek to uncover the rela- 
tionship between the neural changes that under- 
lie amblyopia and the perceptual consequences 
of the disorder. We are currently pursuing the 
idea that the relatively mild type of amblyopia 
typically produced by anisometropia (having un- 
symmetric parts) involves a deficit in the P sys- 
tem, while the more complex syndrome that of- 
ten follows strabismus also involves important 
deficits in the M system. 
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