SUBCORTICAL mechanisms which influence the electrical activity of the cerebral cortex have been widely investigated since the earlier work of Bremer * and Dempsey and Morison,3 by Jasper and coworker,4 Moruzzi and Magoun5 and others. "Activation," or the evocation of an alerting effect on cortical potentials by stimulation of the reticular formation and hypothalamus, and evocation of recruiting responses by stimulation of reticular formation, thalamus, and some basal ganglionic structures have been extensively studied, especially by the groups of Magoun and Jasper. It has been shown, on the contrary, that suitable lesions in the hypothalamus and thalamus and extensive destruction of upper midbrain tegmentum profoundly affect spontaneous cortical potential patterns and produce behavior changes in animals and man (Ingram and associates,6 Lindsley and associates,7 Meyer and Hunter,8 and Baird and associates9). The impulses producing activation apparently pass from reticular formation and hypothalamus by way