Fisk, G.D., & Wyss, J.M. (1999). Associational projections of the anterior midline cortex in the rat: Intracingulate and retrosplenial connections. Brain Research, 825, 1-13.
Past studies indicate that distinct areas of anterior midline cortex in the rat contribute to diverse functions, such as autonomic nervous system regulation and to learning processes, but the anatomical substrate for these functions has not been elucidated completely. The present study characterizes the associational connections within the midline cortex of the rat by using the anterograde transport of Phaseolus vulgaris leucoagglutinin and Fluororuby. The prelimbic area and the rostral part of the anterior cingulate area (both dorsal and ventral subdivisions) are extensively interconnected with each other. In addition, the caudal half of anterior cingulate cortex has extensive projections to precentral medial cortex and caudally directed projections to retrosplenial cortex. Other cortical areas within anterior midline cortex have relatively limited cortical-cortical projections within this region. The infralimbic, dorsal peduncular, and medial precentral cortices have dense intrinsic projections, but have very limited or no projections to other areas in the anterior midline cortex. Although it has been suggested that cortical-cortical projections from anterior cingulate cortex and prelimbic cortex to infralimbic cortex may be important for linking learning processes with an autonomic nervous system response, the paucity of direct projection between these areas does not support this possibility. Together with previous studies of this region, these data suggest that the anterior cingulate and prelimbic areas of anterior midline cortex, which are important for learning and memory, are likely to be functionally distinct from the infralimbic and dorsal peduncular cortices, which are more likely to be involved in modifying autonomic nervous system activity. If these regions interact to produce or extinguish conditioned emotional responses, they must do so via projections to a common subcortical target site.