[The effect of sombrevin on the orientation adjustment of the visual cortex neurons in the cat]

Change in the orientation tuning of 58 visual cortex neurons, evoked by LIGHT sombrevine anaesthesia were studied in acute experiments on immobilized cats. After the sombrevine injection a reliable change of the preferable orientation by 47.6 +/- 5.6 degrees took place in 60% of cells, while in the remaining cells it was stable in all stages of anaesthesia. Stable neurons preferred the horizontal and vertical orientations, in the unstable ones this preference was less expressed. The stable neurons possessed higher qualities of orientation detection than the unstable ones. The width of the orientation tuning changed reliably by 65.2 +/- 6.7 degrees on the average in 55% of neurons, while in 31% of neurons the tuning acuteness was worse, but in 24% it was sharper. The frequency of background discharges under anaesthesia in 2/3 of investigated neurons was reduced by 58% and that of the evoked discharges by 35%. The preferable orientation, the width of the tuning and the frequency of the neuron discharge as a rule recovered in 30 min after the beginning of the anaesthesia.