新皮質系と大脳辺縁系との機能的連関

Functional Correlation between Neocortical and Limbic System

I．はじめに

　近年，旧皮質paleocortex（梨状葉）と古皮質archicortex（海馬）を主体とする大脳辺縁系limbic systemの脳機能に対する役割が重要視されるようになり，同時にまた，大脳辺縁系の活動水準を支配する賦活系についても，新しい事実が集積されてきている。

　そこで，当然問題になることは，新皮質系neocortical systemと大脳辺縁系の機能的連関である。この問題にはいる前に，新皮質系と大脳辺縁系の構成について説明しておこう。

The role of the midbrain reticular formation and hypothalamus and the functional correlation between these two structures in activating mechanism for the cerebral cortex were studied in Flaxedil immobilized cats, by means of simultaneous recording of EEG from the neo- and limbic cortices. In cerveau isole preparation, the neo- and limbic cortices showed sleep and arousal patterns respectively, and stimulation of the hypothalamus exhibited the activating effect only upon the limbic cortex. In this preparation the same results were also obtained by injection of adrenaline or inhalation of carbon dioxide. On the other hand, a stronger stimulation of the hypothalamus on the intact brain produced activation patterns in the neocortex as well as limbic cortex. From these results, it may be reasonablly considered that the midbrain reticular formation contains the activating mechanism only for the neocortex, while the hypothalamus includes the activating mechanism not only for the limbic cortex, but also for the neocortex via the hypothalamo-midbrain route. This backwards activating effect upon the reticular formation from the hypothalamus will provide the functional correlation between the neocortical and limbic system. This assumption is supported from the fact that the changes in the wave forms of the evoked potential and discharge patterns of strychnine spikes on the neocortex correspond to change of hippocampal EEG patterns which is demonstrated to be an indicator of the activity level of the hippo-campus.