Physiological changes during operations on the limbic system in man

The limbic system is a phylogenetically old part of the brain which is concerned with a variety of emotional and viscerosomatic functions. It has been found that small discrete lesions, placed by stereotaxis in this system during limbic leukotomy, may result in marked clinical improvement in severely incapacitated psychiatric patients who have failed to respond to any other type of treatment. In one patient, electrical stimulation of the anterior cingulate gyrus was carried out under local anesthesia to locate a suitable site for a limbic lesion. Physiological arousal was produced, as evidenced by changes in heart rate, forearm blood flow, sweat gland activity and respiration. Bilateral lesions, 8 mm in diameter, produced by freezing this site, resulted in marked clinical improvement. Peripheral physiological changes are now being used to aid in the selection of target sites in various parts of the limbic system. Under general anesthesia marked respiratory changes have been found on stimulation of the lower medial quadrant of the frontal lobe, anterior cingulate gyrus, above the roof of the lateral ventricle, and in the amygdala nucleus of the temporal lobe. Lesions are made with a cryogenic probe at sites of maximum physiological response. It is postulated that physiological monitoring during electrical stimulation of target areas will improve the accuracy of lesion placement. Some of the results of this procedure are described.