Receptive-field properties of different classes of neurons in visual cortex of normal and dark-reared cats

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Abstract
The receptive-field properties of visually responsive striate cortical neurons were studied in 15 normal adult cats and in 7 cats reared in darkness for 7-12 mo. from birth. Three classes of cells were described. Prolonged dark-rearing reduced the visual responsiveness and increased the response variability of all types of neurons studied. Evidence does not suggest that the decrease in direction sensitivity of all cell types and the loss of orientation sensitivity of LAS [large area-slow] and F [fast] cells are simply the result of a drop in visual responsiveness, but rather that many nonselective neurons in dark-reared cats lack inhibitory inputs which, in normal animals, give rise to selectivity. Inhibitory connections in the mammalian visual system may be especially dependent on visual experience for the development or maintenance of normal function. Perhaps LAS cells receive afferent inputs from W-cells in the dorsal nucleus of the lateral geniculate body (LGNd), SAS [small area-slow] cells receive afferent inputs from X-cells in the LGNd, and F cells receive afferent inputs from Y-cells in the LGNd. Consistent with this, the relative number of LAS cells and of SAS cells is high near the cortical projection of the area centralis, and is low in more eccentric regions; the converse is true for F cells. This meshes well with the distribution of W-, X- and Y-cells in the retina and LGNd. In addition, LAS cells occur in layers II-IV of area 17, SAS cells occur most often in layer IV, and F cells are concentrated in the deeper cortical layers. This is consistent with the laminar distribution of LGNd W-, X- and Y-cell terminals for area 17. It is proposed that LAS, SAS and F cells are cortical extensions of the excitatory W-, X-, and Y-cell pathways. It is also suggested that the reported unique susceptibility to binocular competition of Y-cells in the LGNd may result from the difference in binocularity of LAS, SAS and F cells in the visual cortex. The preferential response of the visual system to horizontal and to vertical patterns may be determined intrinsically, and may reflect the response properties and distribution of certain cortical neurons, possibly a subset of those cells that receive afferent inputs from X-cells in the LGNd.