RELATIONSHIPS BETWEEN DENDRITIC FIELDS AND FUNCTIONAL ARCHITECTURE INSTRIATE CORTEX OF NORMAL AND VISUALLY DEPRIVED CATS

We examined relationships between the pattern of geniculocortical inne rvation and the dendritic fields of cells in layer 4 of in cat primary visual cortex, Experiments were performed on normal animals and on ca ts in which the geniculocortical projection was altered by monocular d eprivation or by the induction of divergent squint during the critical period. Thalamic afferents providing the input from the contralateral eye were anterogradely labeled by injecting the fluorescent tracer Di l into lamina A of the lateral geniculate nucleus, Intracellular stain ing with Lucifer yellow in slice preparations allowed simultaneous vis ualization of the morphology of individual cells and the thalamic affe rents, Our results demonstrate that spiny stellate cells close to the upper and lower margin of the geniculocortical input have highly asymm etric dendritic fields, and thereby confine their dendrites to the ter mination zone of these afferents, This effect was specific for the cel l class; it was not observed in pyramidal neurons, These dendritic asy mmetries perpendicular to the laminar borders of spiny stellate cells were not altered by monocular deprivation or strabismus, In contrast, visual deprivation strongly influenced the dendritic arbors of spiny s tellate cells near the borders between adjacent ocular dominance colum ns. In normal animals, the dendrites of cells near columnar borders re mained preferentially within one column, These dendritic asymmetries b ecame much more pronounced in strabismic animals, Monocular deprivatio n weakened the influence of the columnar borders on dendritic fields, Spiny stellate cells within the columns of the open eye exhibited a sl ight tendency to confine their dendrites to these columns, Cells in th e columns of the deprived eye showed the opposite effect; they extende d their dendrites preferentially into the adjacent columns of the open eye, These results demonstrate that the segregation of geniculocortic al afferents into ocular dominance columns and its perturbation by man ipulation of the Visual input plays an important role in defining the morphology of cortical target cells, Thus, activity-dependent structur al changes not only occur at the level of the presynaptic terminals, b ut also at the level of the postsynaptic target cells, and thereby con tribute to build up the functional architecture of the cortex.