Changes in neocortical function in response to the direct action of optical radiation.

The action of optical radiation on neocortical bioelectrical activity and on a penicillin-induced epileptic focus was investigated. The direct action of ultraviolet (UV) radiation with wavelengths 280, 310, and 365 nm was shown to increase the amplitude of the spontaneous EEG and to potentiate epileptiform activity, whereas the action of subthreshold radiation with wavelengths of 580 and 630 nm caused a reduction of EEG amplitude and inhibition of epileptiform activity. On the basis of the writers' own results and data in the literature it is postulated that the mechanism of action of UV radiation on neocortical electrical activity is based on changes in permeability of neuronal membranes to Na and K ions and subsequent membrane depolarization, whereas the action of visible radiation leads to thermal injury to the neurons in the irradiated zone, inducing irreversible suppression of their activity and a decrease in amplitude of the EEG.