IN THIS symposium, Professor Magoun has described some of the properties of the reticular system of the brain stem, with particular reference to mechanisms underlying alertness or arousal of the organism and its effect upon the electrical activity of the cortex. Emphasis has been placed upon that portion of this system lying in the basal part of the diencephalon and midbrain, with some extension into the mesial portion of the thalamus. From the results presented it would seem that the ascending portion of the reticular system in the more caudal part of the brain stem exerts its effect upon the electrical activity of the cortex in a generalized manner, without evidence of topographic localization.
In the thalamus there exists a more highly differentiated portion of this system, which we have tentatively described as the thalamic reticular system. Electrical stimulation within this system is capable of exerting a similar activating influence