| Popis: |
An inhibitory system is described which effectively counteracts the “arousal” system described by Moruzzi and Magoun. Although anatomically it includes the caudate and the non-specific thalamic nuclei, thus partly overlapping with the “arousal” system, its effect depends on a low frequency input. If this input reaches a threshold intensity, both spindle bursts and behavioral inhibition simultaneously occur. The electrophysiological response, as well as its behavioral correlate, can be simultaneously eliminated by a superimposed high frequency stimulus to the same structures. Behavioral inhibition was only seen when spindle bursts were present. The existence of an inhibitory circuit is proposed in which the caudate nucleus figures prominently. It balances and counteracts the system of Moruzzi and Magoun and thus plays an important role in wakefulness, attention, integration, discrimination, and learning. The balance can be maintained or shifted in a given direction, independently of the total input to the brain. It was thus shown that the effects of stimulation of large areas in the brain depend on the frequency of the input as much as on anatomical location or total intensity of input. |
