FUNCTIONAL AND STRUCTURAL ABNORMALITIES O F VISUAL-CORTEX IN INFANTILE STRABISMUS

Background To investigate the structural basis for functional deficits in infantile strabismus we used a neuroanatomic tracer and a histoche mical label to examine the primary visual cortex (area V1) of adult es otropic macaque monkeys.Animals and methods The animals had developed natural esotropia in the first months of life, alternated fixation, an d exhibited the ocular motor signs that typify strabismus with onset i n infancy. After behavioral and VEP testing, ocular dominance columns (ODCs) in V1 were injected with a neuronal traser and labeled for cyto chrome oxidase activity. Results The strabismic monkeys showed strikin g deficits in binocular luminance visually-evoked potentials (VEPs) an d characteristic directional asymmetries in motion VEPs. Binocular hor izontal connections between ODCs were reduced an average of 50-60% in strabismic as compared to normal monkeys. ODCs also showed unequal met abolic activity with contralaterally (i.e. nasal retina) driven ODCs s howing greater activity in each V1. Discussion and conclusion The mald evelopment of connections in upper V1 layers correlates with the abnor malities in binocular and motion VEPs. The unequal metabolic activity suggests interocular suppression. These results provide the first neur oanatomic evidence for cerebral cortex maldevelopments in natural infa ntile esotropia.