The presence in the hypothalamic region of the brain of a central representation of the autonomic nervous system (Karplus,1 Bard2 and Ranson3) implies the existence of a descending pathway or collection of paths transmitting influences from this region to lower centers and thence to the peripheral nervous system.
Some evidence as to the location within the brain stem of such a descending connection has been presented by Beattie, Brow and Long,4 who studied the degeneration following lesions which injured the posteromedial part of the hypothalamus and the rostral portion of the midbrain just behind this region and thus interrupted the periventricular outflow from the posterior part of the hypothalamus. After such lesions, some fibers were followed into the rostral portion of the mesencephalic tegmentum, where they became lost, but the main body of degeneration was traced caudad in relation to the central gray matter of the
H. W. MAGOUN, S. W. RANSON, A. HETHERINGTON. DESCENDING CONNECTIONS FROM THE HYPOTHALAMUS. Arch NeurPsych. 1938;39(6):1127–1149. doi:10.1001/archneurpsyc.1938.02270060017001