Photosensitive waves in the cat's visual system.

Abstract

Using curarized cats under artificial respiration, the following observations were made.1. In the dark room, 3-7/sec regular sinusoidal waves spontaneously appeared in the lateral geniculate body, optic tract, and in some cases in the cortical visual area, sometimes immediately after, and mostly from 30-minutes to several hours after the insertion of the depth electrodes.2. These waves were blocked by illumination abruptly, and after the cessation of illumination, with latency of less than 1-3 sec, sinusoidal waves reappeared. In the pretectal area, these waves were hardly observed. Sometimes under illumination, bright rhythm of higher frequency appeared.3. These waves appeared easily, especially during nitrous oxide gas inhalation, or after the administration of ethyl alcohol and, though it was less frequent, after the administration of small dose of pentobarbital.4. These waves were not abolished after the unilateral cutting of the optic tract (ipsilateral or contralateral) or one side enucleation of the eye ball, but waxing and waning phenomenon was diminished after one side cutting. After cutting of the bilateral optic nerves, 3-7/sec synchronized waves did not appear.5. These waves were hardly influenced by reticular or hypothalamic stimulation, by peripheral nerve and noxious stimulation. Stronger stimulation, suppressed these waves with relatively longer latent period (1-2 sec) and desynchronized to the low voltage fast activity.6. Localized activation of the visual cortex by high frequency electrical stimulation of the optic tract, lateral geniculate body and pretectal area or by photic stimulation was considerably difficult in contrast to the relative easiness of localized activation in the auditory cortex.7. In the preparation with both optic nerves cut, though photosensitive synchronized waves did not appear, electrical stimulation of the optic tract and lateral geniculate body easily elicited in the lateral geniculate body and visual cortex ca.10/sec waves.Stronger stimulation of the reticular formation also produced the similar waves in the lateral geniculate body. From these findings the different characteristics of the electrical activity in the visual system compared to other cortical and subcortical areas were discussed.These results were reported in the 133rd Meeting of Tokyo Association of Japan Physiological Society in October 10, 1959 and in the 11th Annual Meeting of the Japan EEG Society in 1960.The authors wish to express their sincere thanks to Prof. T. TOKIZANE for his valuable suggestions, and to Miss M. TAKAHASHI for preparing histological sections.