The Posteromedial Cortex across Species

Abstract

The posteromedial cortex (PMC) is the posterior hub of the default mode network, made up of the posterior cingulate cortex, retrosplenial cortex, and the precuneus. Despite the default mode network’s relevance in psychiatric disease states, not much work has been done to evaluate multimodal connectivity of the PMC in nonhuman animals. The cortico-striatal and cortico-cortical connections of the PMC in rats and macaques are found through anatomical tract-tracing techniques. Then, anatomical cortico-striatal connections are compared to functional connectivity obtained through resting state functional MRI (rs-fMRI) in the macaque. Anatomical connectivity demonstrates that both the rat and macaque PMC project to the dorsomedial striatum, which is considered to be involved in goal-directed decision making. When looking at the overlap of striatal territory among frontal cortex, both species have overlap with the anterior cingulate cortex and lateral orbitofrontal cortex. Differences in striatal territory overlap include prelimbic cortex and medial orbitofrontal cortex in rat, and dorsolateral prefrontal cortex in macaque. In addition to similar cortico-striatal connectivity, the cortico-cortical connections are also similar between species; the PMC is highly connected to the anterior cingulate, and also is connected to the orbitofrontal cortex. In macaques, the functional connectivity of the PMC has a weak relationship with the anatomical activity, a finding that may relate to its function as an association area.