[Activation response to photic stimulation in normal cats and after transection of the afferent pathways of the mesencephalic reticular formation].

In chronic experiments on waking unrestrained cats with implanted electrodes the reaction of EEG activation to light stimulation was recorded in two sets of experiments in normal cats and in animals with transsection of brachia colliculi superioris that separated mesencephalic reticular system. The intensity of the activating reaction in the intact cats increased ith a rise in the light stimulus intensity. In the cats with brachia-colliculi superioris transsected there was no definite dependence on the stimuli intensity and the intensity of the activating reaction changed randomly. It is suggested that this irregularity is accounted for by blocking of the excitating afferent flow usually coming to the mesencephalic reticular formation through brachia and colliculi both from the visual pathways (ascending flow) and from the cortex (descending activation regulating flow).