Strabismus and visual suppression
Start date: 01 Sep 2007,
End date: 31 Aug 2009
Strabismus is a common childhood disease, characterized by a failure to align the eyes. Interestingly, few strabismic children complain of double vision. Many may simply be too young to articulate their perceptions, but another critical factor is that children rapidly suppress vision in the deviated eye.This suppression prevents eye alignment by eliminating the error signal that would normally induce adjustment of muscle tone to bring their eyes back together. In addition, suppression generates amblyopia, a cause of permanent visual loss. The principal focus of this research proposal will be to discover how and where in the brain, strabismic suppression occurs. This objective will be achieved with a combination of complementary techniques. Strabismic humans will partake in psychophysical experiments, designed to map regional suppression.They will then participate in a brain imaging (fMRI) experiment, to reveal how suppression affects neuronal activity in the visual system. This experiment will uncover both the neural signature of strabismic suppression, and where in the brain it is generated. fMRI is an excellent technique to gauge the strength and location of brain activation.However, it sheds less light on the temporal characteristics or the nature of the observed activity. For this reason, an electrophysiological experiment in awake monkeys with experimental strabismus will be done in tandem. The precise temporal and spatial resolution afforded by single unit recording will enable us to monitor how the responses of single visually driven cells change, as they either signal perception or are suppressed.This multidisciplinary approach will be necessary to produce a complete description of the problem of suppression in strabismus. It is our conviction that a better understanding of the neural mechanism of strabismic suppression will permit the development of improved strategies for the effective treatment, or even prevention of strabismus in children.
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