ON THE SLEEP INDUCED THROUGB ELECTRICAL STIMULATION ON DOG THALAMUS
Authors: Akimoto Haruo , Yamaguchi Nariyoshi , Okabe Ken‐ichirô , Nakagawa Tsutomu , Nakamura Itsuaki , Abe Ranichi , Torii Hosaku , Masahashi Kôji 
Published: March 2008

Sleep was induced in dogs by a repetitive stimulation of low frequency (about 5C./sec.) low voltage (3 V.) current on the animal's thalamic inkgrating system. This experimental sleep is termed “thalamogenic sleep”.

By taking simultaneous records of both cortical and subcortical EEG during the experimental sleep and giving it an electroencepha‐lographic interpretation, and further comparing it with the EEG patterns of the normal sleep and of that under barbiturate narcosis, the following results were obtained:

1. The EEG records of a wake and resting animal consist of irregular patterns of low voltage (7–15C./sec.) waves showing no such rhythm resembling the aL rhythm in man. The EEG pattern from 20 th sec. after the beginning of stimulation gradually gets increased in the amplitude, and turn to slow waves. This change is more marked in the subcortex. From about 30 th sec. on, spindle bursts of about 12C./sec. appear synchronously at relatively regular intervals in the cortical motor area and somato‐sensory area. As a rule, spindle bursts are not detectable in the subcortical record, only occasionally accompanied by some superposing slow waves.

With the advance of sleep, appearance of the spindle bursts gets rarer and, instead, high voltage slow waves of 1–3C./sec. predominate. These slow waves come out again more marked in the sulxortical EEG, wherein there are seen the succession of the voltage waves with amplitude often raised up to 330μV. The cessation of the stimulation at this moment does not cause the slow waves to disappear.

2. The changes in the animal's behavior go nearly parallel with those in the EEG pattern. Particularis noticeable is the coincidence of both features under wake state. When the thalamic integrating system is activated with a stimulation of high frequency (30–90C./sec.), the animal wakes up and the EEG begins to show the arousal waves with that.

3. With pulse duration kept constant, the factor which determines the variance between sleep and activating reactions is represented by frequency. By altering the frequency we are able to obtain both the sleep reaction as well as the activation reaction from the same portions at will.

4. Dog's EEG and the process during the sleep induced by an electrical stimulation on thalamus agrees with the KEG and the process seen in the natural sleep, but different from those under barhiturate narcosis. Consequently, it is reasonable to regard the sleep caused by electrical thalamic stimulation as an induced form of the natural sleep, judged both from the clinical and the electroencephaloyraphic findings.

5. At present we interpret the mechanism of thalamogenic sleep as follows: It is no other matter than synchronization of the diffuse cortical activity originated in the thalamic integrating system. This synchronization of the thalamic integrating system goes propagated not only to the cerebral cortex but also to the various sukortical regions, namely; striatum, hypothalamus and midbrain. This agrees with the fact that sleep is a functional depression not only of the cerebral cortex but of the whole brain including subcortex.

Since synchronization of EEG is no other matter than the functional inhibition, thalamogenic sleep may be regarded as an extension of inhibition originated in the thalamic integrating system to the cerebral. cortex and subcortex.