Telencephalic Projections of the Midline and Intralaminar Nuclei in the Cat **

Since 1942, when Morison and Dempsey' first published the finding that stimulation of certain subcortical structures in the region of the internal medullary lamina resulted in widely distributed "rhythmically recurrent cortical potentials," there has been a steadily increasing interest in the physiological and anatomical parameters of this so-called "recruiting response." Subsequent investigations by Jasper'0 and by Starzl and Magoun" bore out, in general, the initial results of Morison and Dempsey but differed to a certain degree as to which cortical areas were affected and which subcortical structures, when stimulated, elicited the "recruiting response." The group of subcortical structures includes, according to most investigators, the midline and intralaminar nuclei, the centrum medianum, the anterior nucleus, and the anterior portions of the reticular complex of the thalamus. However, cortical activation has also been reported by some authors upon stimulation of the n. ventralis anterior,a n. medialis dorsalis,1 n. reuniens,l° n. parafascicularis," n. postero-lateralis," and the pulvinar.' It has been postulated that the nuclei from which recruiting phenomenon can be elicited are the diencephalic components of a "central activating system"'t or "centrencephalic system"'t which would, by modulating all