Visceral Circuits and Cingulate-Mediated Autonomic Functions

Abstract Involvement of cingulate cortex in visceral function has been long known. The classical electrical stimulation studies of Smith (1945), Pool and Ransohoff (1949), and Kaada (1951) provided a rich substrate of information showing that anterior cingulate cortex (ACC) was part of a broad swath of orbitofrontal, insular, and temporal pole cortex that regulates visceral functions. In spite of technical issues relating to the intensity and duration of stimulation, these investigators showed that autonomic responses were not the result of current spread from the cingulate gyrus because electrical stimulation in adjacent cortex did not produce such changes and ablation outcomes were as predicted. Most importantly, subsequent studies such as those of MacLean (1990) and Talairach et al. (1973) confirmed autonomic and skeletomotor responses and circuitry studies showing cingulate projections to visceral autonomic nuclei, the lateral hypothalamus (LH), periaqueductal gray (PAG), and intermediolateral nucleus of the spinal cord (IML) provided mechanisms to support the conclusion that evoked responses originated in cingulate cortex and were not due to current spread. A new generation of mechanistic studies in rodents emerged in the 1980s and 1990s in conjunction with very precise connection studies and validated the concept that autonomic activity could be generated by electrical stimulation of the subgenual ACC (sACC) and some of the subcortical intermediates to autonomic motor centers.