Sustained and transient cells in monkey lateral geniculate nucleus: conduction velocites and response properties.

The receptive-field properties of units in the macaque LGN were studied with extracellular microelectrodes. Analysis of responses of opponent and nonopponent cells to stationary spots, moving spots, and grating revealed transient and sustained varieties of both spectral groups as well as cells with mixed properties. The cell's temporal discharge pattern was not correlated with its color sensitivity. Cells that ere classified as sustained responders did so under all stimulus conditions tested. Most transient cells responded in a transient fashion to each stimulus tested. In a few cells, a sustained response could be shortened into a transient response by activating the cell's surroun mechanism. The conduction velocities of sustained and transient cells were determined by shocking optic chiasm and striate cortex. Among nonopponent cells, transient types conducted significantly faster than the sustained type. No such difference was found among opponent cells. Among all cells, the fastest conducting were transient nonopponent (14 m/s), while the slowest were +B-Y opponent cells (4 m/s). Intermediate were sustained nonopponent (11 m/s) and the remainder of opponent cells types (about 7 m/s). There was a significant positive correlation between a cell's shock-evoked spike latency and its visually evoked latency. These results suggest that there are at least three independent information channels in monkey geniculostriate pathway. Further characterization of these channels is in progress.