[Orientation tuning of the visual cortex neurons in the cat before and after nembutal injection]

In acute experiments on immobilized cats orientation tuning of 40 neurons in the primary visual cortex (field 17) has been studied before and after nembutal injection. It was found that the preferred orientation (PO) of half of neurons remained constant after injection, while another half of neurons revealed a reliable shift of PO (by 53.6 +/- 8.0 degrees on the average) during 1 min-3 hours. Neurons with constant PO preferred horizontal and vertical orientations more often, while neurons with unstable PO had wider distribution of their POs. "Stable" neurons had more narrow and selective orientation tuning before and after narcotization than the "unstable" ones. After injection of nembutal, the width of orientation tuning changed in a half of neurons; this was more often expressed in "unstable" neurons (68%), than in the "stable" ones (38%). After narcotization the mean background discharge frequency decreased 5.5 times on the average in all neurons, while the evoked frequency of discharges--1.5 times.