Effects of visual deprivation upon the geniculocortical W-cell pathway in the cat: area 19 and its afferent input.

We studied the receptive field properties of 206 single units in area 19 of normal cats and 228 single units in area 19 of cats deprived of vision for 9-14 months by monocular lid suture. The ocular dominance of a sample of cells in area 17 of normal cats was studied for comparison. In some of these monocularly deprived animals, we also studied the sizes of relay cells in the parvocellular C laminae of the dorsal lateral geniculate nucleus labeled by electrophoretic injections of horseradish peroxidase into area 19. In area 19 of normal cats, the large majority of cells, regardless of their laminar location and the retinal eccentricity of their receptive fields, were binocular. Most responded equally well to the two eyes. In area 17, (see also Leventhal and Hirsch, '78, '80) but not in area 19, the cells which had the narrowest receptive fields tended to be activated unequally by the two eyes. In area 19 of monocularly deprived cats, virtually all cells (97%), regardless of their laminar location and receptive field eccentricity, responded only to stimulation of the normal eye. Thus, the effects of monocular deprivation upon area 19 are apparently more severe than those reported for area 17. In area 17 significant numbers of neurons in layer 4 can be activated by the deprived eye (Shatz and Stryker, '78). Within the limits of our technique, measurements of relay cells in the parvocellular C laminae labeled by injections into area 19 of deprived cats indicated that cell size in the deprived C laminae was unaffected by the deprivation. In contrast, cells in the deprived A laminae of these cats were severely shrunken. These findings suggest that the types of relay found in the parvocellular C laminae (referred to collectively as W-cells) are not affected by visual deprivation as severely as are the X- and Y-cells in the A laminae. Since laminar location and receptive field width are related to binocularity in area 17 but not in area 19 and the sizes of relay cells in the parvocellular C laminae (see also Hickey, '80) are not seriously affected by monocular deprivation, it is suggested that binocular interactions in area 19 are mainly determined by connections among cortical cells.