In neurophysiological studies, the motor system is modeled as a distributed, often hierarchical system with the spinal cord controlling the "most automatic" of movements such as stretch reflexes, and the cortex controlling the "most voluntary" actions such as reaching for an object, with the brainstem performing a function somewhere in between the two.
Hobson and McCarley hypothesized that a brain stem neuronal mechanism sends pontine-geniculo-occipital (or PGO) waves that automatically activate the mammalian forebrain.
He and his collaborators have developed the first neurorobotic system in which a neural preparation in-vitro - the brainstem of a Lamprey - controls the behavior of a mobile-robot through a closed-loop interaction.
In a 1957 experiment, physiologist Walter Hess used an electrode to stimulate a certain part of a resting cat's brainstem; immediately after the stimulation, the cat stood up and arched its back with erect hair - a species-typical behavior in which cats engage when frightened.