Electrical Stimulation of Points in the Forebrain and Midbrain

There has been a great deal of interest in recent years in the vegetative centers of the hypothalamus. Various investigators1have stimulated this region and reported dilatation of the pupils, increased blood pressure, contraction of the bladder and increased rate and depth of respiration as well as effects on gastro-intestinal peristalsis and secretion of sweat, saliva, tears, etc. The localization obtained was not precise, however, and no attempt was made to trace the pathways by stimulation. An extensive investigation was therefore undertaken in this laboratory into the responses of the hypothalamus to electrical stimulation. During this investigation the brain was explored millimeter by millimeter from a level close to the junction of the olfactory bulb and tract as far caudally as a plane through the inferior colliculi dorsally and the middle of the pons ventrally. The Horsley-Clarke stereotaxic instrument was used to orient the electrodes. By stimulation of large