Comparison of receptive-field properties of X and Y ganglion cells with X and Y lateral geniculate cells in the cat

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Abstract
To examine the transmission of visual information through the lateral geniculate nucleus, the receptive-field properties of 65 X and Y optic tract axons were studied and compared with the receptive-field properties of X and Y LGN (lateral geniculate nucleus) cells in paralyzed cats anesthetized with N2O/O2 (70/30%). The same experimental conditions and quantitative methods have been used as in the preceding study of LGN cells. The spatiotemporal organization of the receptive fields of X and Y retinal axons are similar to those of X and Y LGN cells. X ganglion cell receptive fields show a simple center-surround organization, whereas Y ganglion cell receptive fields show a more complex organization with 3 concentric regions: a central region of center-type response, a region of mixed center-type and surround-type responses and a region of surround-type response. The inhibitory strength of the surrounding region was tested with a centrally located flashing light spot of successively increased diameter. The decrease of the inhibitory strength of the surrounding region with increasing distance from the receptive-field center was similar in the retina and in the LGN for cells belonging to the same class (X or Y) and having the same receptive-field center size. The differences in properties in the LGN between small-field X-, large-field X- and Y-cells are best explained by assuming that they are driven, respectively, by small-field X, large-field X and Y retinal ganglion cells. The principal transformation between retinal and LGN units is that X LGN cells have sharply lower spontaneous activities and driven activities, as compared with X ganglion cells. Y LGN units show only a small decrease in spontaneous activity in comparison with Y ganglion cells. There is probably a significant alteration in the LGN only in the properties of X-cells, possibly by way of a strong inhibitory pool converging on X LGN units. This inhibitory pool apparently plays a role in the modulation of transmission of information through the LGN only in the X channel, while the Y channel appears to be relatively unaffected.