Spatial analysis of ocular dominance patterns in monocularly deprived cats

Monocular deprivation during a critical period in postnatal development leads to a shift in functional and anatomical ocular dominance at the expense of the deprived eye. We analyzed the complete two-dimensional pattern of [(3)H]proline-labeled afferents in primary visual cortex (area 17) of cats monocularly deprived of vision at eye opening. Substantial shrinkage of deprived eye territory in favor of the normal eye extended into optic disc and monocular segment representations. However, small domains of deprived eye afferents were distributed evenly over the entire visual field representation. Interestingly, normal and deprived eye afferents overlapped extensively in the ipsilateral and in the peripheral contralateral visual field representation of the deprived eye, so that ipsi- and contralateral ocular dominance patterns are not at all complementary. We suggest that this could be the result of both an earlier maturation of crossed versus uncrossed visual pathways and of a maturational gradient within area 17 leading to a lower vulnerability of the central visual field representation to monocular deprivation. Quantitative analysis, using a triangulation algorithm which confirmed previously described larger spacing of adjacent ocular dominance columns in strabismic cats, revealed no difference in spacing of ocular dominance domains in area 17 between monocularly deprived and normals cats. In addition, column spacing was very similar in the same animal and in littermates, indicating that the genetic influence on columnar layout is stronger than previously assumed.