Diagonal ventral forebrain continuum has overlapping telencephalic inputs and brainstem outputs which may represent loci for limbic/autonomic integration.

Growing evidence indicates that three areas within the mammalian basal forebrain share many common features. Based on the similarity of connections and their adjacent spacial proximity, three forebrain nuclei are referred to as a continuum. The components of this diagonal ventral forebrain continuum (DVFC) are the central nucleus of the amygdala, the sublenticular portion of the substantia innominata, and the lateral bed nucleus of the stria terminalis. A primary concern and terminal goal of this study is to determine whether the region of this continuum which projects to the brainstem autonomic nuclei such as the vagal nuclei or the parabrachial nuclei also receives inputs from the basolateral amygdala. The first phase of this study involved determining what autonomic regions receive projections from the basal forebrain. The vagal complex and the parabrachial nuclei were found to receive the densest inputs from the DVFC. The topographic distribution of the respective retrogradely labeled cells and their collateral status is described. The second phase involved looking at afferent inputs from brainstem nuclei. The parabrachial nucleus sends reciprocal projections back to the continuum, which generally overlap the neurons which project back to the brainstem visceral nuclei. The third phase of the study indicated that the cells of the basolateral amygdala contribute a major terminal field which overlaps those cells of the basal forebrain continuum which in turn project to either the nucleus of the solitary tract or the parabrachial nucleus. The possibility that the circuits implied in this study represent the neural circuitry whereby emotional stimuli result in changes in visceral activity is addressed.