The Functional Responses of the Sympathetic Nervous System of Man following Hemidecortication.

THE relation of the cerebral cortex to the activity of the sympathetic nervous system is not yet fully clear. The clinical and experimental observations, which have recently been reviewed by Kennard (1937), have been conflicting, and there have been few quantitative determinations of the effects of cortical stimulation and ablation upon the functions of the human sympathetic nervous system. Many indices of sympathetic function have been used in the past, peripheral vascular changes, the psychogalvanic response, sweating, pupillary changes, and visceral contraction being the most usual. The " galvanic skin reflex " is dependent on an intact sympathetic nervous system, and may be accurately measured. It has therefore been widely used as an index of sympathetic activity in studies of cortical function. In 1905 Bechterew stimulated the medial part of the anterior sigmoid gyrus in the cat and caused sweating of the pads. The response was greater on the contralateral side. Winkler (1908) obtained a symmetrically equal response to similar stimulation. In 1930 Langworthy and Richter found that faradic stimulation of cortical areas similar to those used by Bechterew lowered the skin resistance of a cat's pads. The response was bilateral, but was greater on the contralateral side. Schwartz (1937) continued the investigation by excising known areas of the cortex in cats, and observed the " psychogalvanic response " to various stimuli for three to six months afterwards. After unilateral removal of the area frontalis agranularis, peripheral pain and stimuli associated with fright caused no response on the contralateral side, but responses to sudden pressure on the limb remained symmetrically equal. Excision of cortex elsewhere did not modify the response in any way, so that Schwartz postulated two types of response-a " segmental galvanic reflex " independent of cortical control and a "psychogalvanic reflex " with a true cell station in the area frontalis agranularis.