Single cell recordings were made from cat lateral geniculate (LGN) neurons while varying the luminance and size of spots flashed in the center of their receptive fields. The major purpose of the study was to describe any transformations of luminance information that occur in the lateral geniculate. Therefore, comparisons were made between the data recorded and previously published data (Winters and Walters, 1970) from single optic tract neurons, obtained under similar stimulus conditions. The on center LGN neurons showed 2 components in their neuronal discharge patterns that were not found in optic tract fibres. First, at intensities near threshold, at the termination of the stimulus there is a long period, lasting for about 300 msec, in which there is complete suppression of neural activity. This silent period is often followed by a brief discharge before the unit returns to its spontaneous level of firing. Second, at intensities greater than 1.4 log units above threshold, there is a brief period after the on transient, in which there is complete suppression of the response. This silent period lasts about 30 msec and is followed by a relatively depressed steady state component. LGN off center cell response patterns were not found to differ from those of optic tract units. Quantitative evidence for these findings is given.
ASJC Scopus subject areas
- Sensory Systems