Afferent projections to the hypothalamic area controlling emotional responses (HACER)

The Mesulam technique for horseradish peroxidase was used to study the subcortical afferent projections to a location in the hypothalamus that has been shown to control the complete cardiovascular (CV) response accompanying a specific emotional behavior. Major projections common to all baboons injected included the lateral septal nucleus; medial, cortical and basal amygdala; the anteroventral third ventricle area; the preoptic areas; the subiculum; the paraventricular nucleus of the thalamus; periventricular gray and the central gray of the midbrain; the midbrain tegmentum; locus ceruleus, parabrachial and raphe cells in the pons; and in the medulla, raphe nuclei, the nucleus of the solitary tract, in and around the dorsal motor nucleus of the vagus, and in the region of the nucleus ambiguus. Other projections in some but not all baboons included the subfornical organ and the midline and dorsomedial nuclei of the thalamus. The nucleus of the diagonal band of Broca was labeled to some degree with all injections but was most heavily labeled with the injection extending more laterally in the hypothalamus. These results fit well with physiological and behavioral studies dealing with neural control of emotional and CV responses and support the concept of an integrative area in the hypothalamus concerned specifically with the control of CV response accompanying emotion.