Receptive-field transformations between LGN neurons and S-cells of cat-striate cortex.

Publisher Website
Google Scholar
Abstract
To determine the functional transformation in the processing step between lateral geniculate nucleus (LGN) and striate cortex, the receptive-field characteristics of 50 directly driven, lamina 4 S-cells were compared with those of a similar number of LGN neurons. Experiments were performed on paralyzed and anesthetized adult cats. By identifying the signature of LGN neurons in the responses of S-cells it was possible to recognize at least 2 and possibly 3 arrangements in the inputs to these cells. Individual S-cell responses could be explained as arising from: a single type (on- or off-center) of LGN neuron, 2 types (on- and off-center) of LGN neurons with their receptive fields placed side by side along the line orthogonal to the optimal orientation 3 types of LGN neuron. Only a small number of S-cells were placed in the latter category. There is doubt about the existence of the tripartite input, since in certain respects the responses of these cells resembled those of cells receiving a single or dual input. In all 3 groups, S-cells were found receiving inputs from either the fast (brisk transient BT) or slow [brisk sustained BS] stream. An estimate was made of the number of LGN neurons contributing to the receptive fields of single S-cells in lamina 4. After making certain assumptions about the distributions of inputs to the S-cell receptive field, it was estimated that the response in each discharge region came from 1-20 like LGN neurons. The receptive-field midpoints of these afferents are scattered over a circular area, whose diameter is equal to the receptive-field center diameter of one of the afferent LGN neurons (0.4.degree. for BS and 0.8.degree. for BT neurons).