Localization and connectivity of rodent equivalent of the primate posterior cingulate cortex (area 23)

The posterior cingulate cortex (mainly area 23) in human and non-human primates is a critical component of the default mode network and is involved in many neurological and neuropsychiatric diseases such as Alzheimers disease, autism, depression, attention deficit hyperactivity disorder and schizophrenia. However, cingulate area 23 has not yet identified in rodents and other lower mammals and this makes modeling related circuits and diseases in rodents very difficult. Using a comparative approach and unique connectional patterns the present study has uncovered the location and extent of rodent equivalent of the primate cingulate area 23. Like in monkeys, area 23 but not adjoining retrosplenial and visual areas in the rats and mice displays strong reciprocal connections with the anteromedial thalamic nucleus. Rodent area 23 also reciprocally connects with the medial pulvinar and claustrum as well as with the anterior cingulate, granular retrosplenial, medial orbitofrontal, postrhinal, and visual and auditory association cortices. The rodent A23 also projects to the subcortical effectors such as the dorsal striatum, ventral lateral geniculate nucleus, zona incerta, pretectal nucleus, superior colliculus, periaqueductal gray, and brainstem reticular formation. All these connectional findings support the versatility of area 23 in the integration and modulation of multimodal information underlying spatial processing, episodic memory, self-reflection, attention, value assessment and many adaptive behaviors. Additionally, this study also suggests that the rodents can be used to model primate and human area 23 in future structural, functional, pathological and neuromodulation studies.