Effects of eliminating retinal Y cell input on center-surround interactions in the dorsal lateral geniculate nucleus of the cat.
The aim of this project was to investigate the interaction between Y retinal ganglion cells and the cells of the dorsal lateral geniculate nucleus (LGNd) of the cat, with particular reference to center-surround antagonism and intrageniculate inhibition. Responses of cells in the LGNd were studied by stimulating the retina with spots of light of constant contrast but varying size. The peak discharges of nonlagged X (XN) cells were strongly suppressed with increase in spot size but the responses of lagged X (XL) cells and nonlagged Y (YN) cells were inhibited much less strongly. The effect of the Y system on these responses was examined by producing a selective block of conduction in Y fibers in one optic nerve by means of a pressure cuff (Y-blocking). These effects were assessed by measuring the peak discharge rates and by calculation of a "peak suppression index." Y-blocking had no significant effect on the peak suppression index of XL cells in either lamina or on YN cells in the normal (not Y-blocked) lamina but had significant effects on the responses of XN cells, causing a decrease in peak suppression index, both for cells in laminae receiving their principal excitatory input from the Y-blocked eye (both lamina A and lamina A1) as well as those in lamina A (but not lamina A1) receiving their excitatory input from the normal eye. These effects were obtained with relatively large spots of light. Thus Y optic fibers have both intralaminar (monocular) and interlaminar (binocular) inhibitory effects on XN cells. In addition to these suppressive effects, the experiments also show that ipsilaterally projecting Y fibers have facilitatory effects on XN cells in lamina A when small spots of light, about optimal size for the XN cell, are used. These results suggest that the Y system plays a powerful role in shaping the responses of XN cells, possibly enhancing visual acuity.
Wang
C
C
Department of Anatomy and Histology, University of Sydney, N.S.W., Australia.
Dreher
B
B
Burke
W
W
D000818:Animals; D002415:Cats; D004594:Electrophysiology; D005829:Geniculate Bodies / Q000502:physiology*; D009412:Nerve Fibers / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology; D009900:Optic Nerve / Q000503:physiopathology*; D012160:Retina / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*