THE NEURAL BASIS OF SUPPRESSION AND AMBLYOPIA IN STRABISMUS

The neurophysiological consequences of artificial strabismus in rats a nd monkeys have been studied for 30 gears. However, until very recentl y no dear picture has emerged of neural deficits that might account fo r the powerful interocular suppression that strabismic humans experien ce, nor for the severe amblyopia that is often associated with converg ent strabismus Here we review the effects of squint on the integrative capacities of the primary visual cortex and propose a hypothesis abou t the relationship between suppression and amblyopia. Most neurons in the visual cortex of normal cats and monkeys can be excited through ei ther eye and show strong facilitation during binocular stimulation wit h contours of similar orientation in the two eyes. But in strabismic a nimals, cortical neurons tend to fall into two populations of monocula rly excitable cells and exhibit suppressive binocular interactions tha t share key properties with perceptual suppression in strabismic human s. Such interocular suppression, if prolonged and asymmetric (with inp ut from the squinting eye habitually suppressed by that from the fixat ing eye), might lead to neural defects in the representation of the de viating eye and hence to amblyopia.