FURTHER STUDIES ON CEREBRAL REPRESENTATION OF PENILE ERECTION: CAUDAL THALAMUS, MIDBRAIN, AND PONS

Abstract

Brain stimula-tion experiments are being conducted on squirrel monkeys in order to map structures involved in penile erection. A further delineation has been made of a region in the midline part of the medial dorsal nucleus in which stimulation is highly effective in eliciting erection. There is evidence that the major effector pathways from this region do not run directly caudally into the midbrain, but descend rostroventrally into the hypothalamus. One such pathway appears to follow the inferior thalamic peduncle to the lateral hypothalamus and then to continue along the course of the medial forebrain bundle to the ventral tegmental area. From this area positive loci are found to lie along a course that turns abruptly in a dorsolateral direction to reach the "intranigral fasciculus" in the substantia nigra and then descends into the ventrolateral pons. From this level the course passes the ventrolateral aspect of the superior olive and then turns medially to a point near the exit of the sixth nerve and lateral to the pyramids. Other positive loci are found in the brachium pontis, periaqueductal region, floor of the fourth ventricle, and anterior medullary velum. Associated behavioral manifestations are described as well as observations on optimum parameters of stimulation, latency of the genital response, and effects of anesthesia.