[Analysis of photic signals by cats according to their intensity following transection of the superior quadrigeminal brachii].

In experiments on cats trained by the motor alimentary conditioned method to discriminate photic stimuli by intensity, EEG changes were studied when differentiating signals of different biological significance before and after transection of the brachii of the superior colliculi. The normal direct proportional dependence of pronouncedness of brain electrical reactions on the complexity of stimuli analysis was disturbed after transection. The operated animals retained only the capacity for a rough differentiation by brightness, the fine gradation of EEG responses to negative signals of different fineness being lost. The disturbance of interaction between the analysing and activating brain systems after transection of the brachii may be due to both the lack of non-specific ascending tonic influences of the midbrain reticular formation on the cortex, and to the destruction of many pathways for corticofugal control of the activity of the brainstem non-specific apparatus.