Kitsuya Iwama

CORTICAL AND RETICULAR EFFECTS UPON EVOKED ACTIVITY OF THALAMIC SOMATOSENSORY RELAY NUCLEUS

Using cats and dogs, effects of cortical and reticular formation stimulation were examined upon the thalamic evoked potential produced by single shock stimulation of the posterior funiculus. Cortical stimulation was done with a single shock applied to the sensorimotor cortex of one side ipsilateral to the thalamic somatosensory relay nucleus which is to be activated by posterior fimiculus stimulation. The reticular formation was stimulated at the mesencephalic level repetitively with shocks of varying frequencies for about 0.1 second.

Some properties of the secondary discharge in cats' sensorimotor cortex

Abstract Various properties of the secondary discharge recorded from the sensorimotor cortex in response to single shock stimulation of the sciatic nerve were studied in cats under barbiturate anesthesia. 1. 1. The most prominent potential change in the secondary discharge complex was a positive wave of 40 to 80 msec having a peak at 60 to 80 msec after sciatic nerve stimulation. 2. 2. The laminar potential distribution of the secondary discharge was studied with regards to the main positive wave. It was found that the positive wave of the surface was represented by the negative wave 0.5 to 1.2 mm below the surface. This laminar potential distribution was found to be quite similar to that observed for the initial positive wave of the primary specific response. 3. 3. Effects of KCl, gamma-aminobutyric acid (GABA) and strychnine were tested upon the secondary discharge by applying the drugs topically to the cortical surface. It was found that the effects of these drugs were exerted upon the secondary discharge in about the same manner as upon the primary specific or sensory response. KCl promptly suppressed the response. GABA augmented the amplitude in the positive direction, presumably due to its suppressing action upon the surface negative potential. Following local strychninization, the secondary discharge became a high-amplitude, triphasic wave which was similar to the spontaneous strychnine spike. 4. 4. Changes in the cortical excitability were measured in relation to the secondary discharge by taking as indices the primary specific response to stimulation of a thalamic relay nucleus and the pyramidal discharge evoked by direct cortical stimulation. While the positive wave of the secondary discharge was displayed, the negative wave of the primary specific response and the evoked pyramidal discharge were markedly augmented, and thereafter they were slightly suppressed for a short time. There was no significant change in the initial positive wave of the primary specific response in any phase of the secondary discharge.

Effects of repeated reinforcements upon electrical activities of the human brain in conditioned reflexes.

Electroencephalographic conditioning was made in human subjects using pure tone and light respectively as conditioned and unconditioned stimulus (CS and UCS). UCS was combined with CS in such a manner that UCS was started about 5 seconds after the onset of CS and was administered continuously for 2 seconds. In the present experiment, special attention was paid to EEG activity of the subject in the resting condition (resting EEG activity) during the course of successive reinforcements.