THE RECENT demonstration that potentials evoked by peripheral afferent stimulation may be conducted corticipetally through the central brain stem and medial thalamus, as well as through the great lemniscal fillets and thalamic relay nuclei, has opened to speculation the physiological function subserved by such central pathways.1 For a number of reasons, it seems feasible to assume that they may be concerned, at least partially, with arousal from sleep or with maintenance of the alert, wakeful state. It has been shown that the region of the central cephalic brain stem, from which potentials evoked by peripheral stimulation can be recorded, is coexistent with that which, when excited by repetitive stimuli, causes arousal of a dormant animal, together with an appropriate change of its electroencephalogram, from a sleeping to a waking state.2 Furthermore, destruction of this region produces a state of chronic unresponsiveness in the subject.3
Analysis of impulses