Connections of the retrosplenial dysgranular cortex in the rat

Abstract

Although the retrosplenial dysgranular cortex (Rdg) is situated both physically and connectionally between the hippocampal formation and the neocortex, few studies have focused on the connections of Rdg. The present study employs retrograde and anterograde anatomical tracing methods to delineate the connections of Rdg. Each projection to Rdg terminates in distinct layers of the cortex. The thalamic projections to Rdg originate in the anterior (primarily the anteromedial), lateral (primarily the laterodorsal), and reuniens nuclei. Those from the anteromedial nucleus terminate predominantely in layers I and IV-VI, whereas the axons arising from the laterodorsal nucleus have a dense terminal plexus in layers I and III-IV. The cortical projections to Rdg originate primarily in the infraradiata, retrosplenial, postsubicular, and areas 17 and 18b cortices. The projections arising from visual areas 18b and 17 predominantly terminate in layer I of Rdg, axons from contralateral Rdg form a dense terminal plexus in layers I-IV, with a smaller number of terminals in layers V and VI, afferents from postsubiculum terminate in layers I and III-V, and the projection from infraradiata cortex terminates in layers I and V-VI. The efferent projections from Rdg are widespread. The major cortical projections from Rdg are to infraradiata, retrosplenial granular, area 18b, and postsubicular cortices. Subcortical projections from Rdg terminate primarily in the ipsilateral caudate and lateral thalamic nuclei and bilaterally in the anterior thalamic nuclei. The efferent projections from Rdg are topographically organized. Rostral Rdg projects to the dorsal infraradiata cortex and the rostral postsubiculum, while caudal Rdg axons terminate predominantely in the ventral infraradiata and the caudal postsubicular cortices. Caudal but not rostral Rdg projects to areas 17 and 18b of the cortex. The Rdg projections to the lateral and anterior nuclei also are organized along the rostral-caudal axis. Together, these data suggest that Rdg integrates thalamic, hippocampal, and neocortical information.

Antipsychotic Drug-Like Effects of the Selective M4 Muscarinic Acetylcholine Receptor Positive Allosteric Modulator VU0152100

“…The effects of VU0152100 on brain activity in multiple regions suggest that actions in areas outside of the basal ganglia may also contribute to the in vivo effects of VU0152100. These findings are consistent with previous evidence that cortical projections modulate DA function in the striatum (Desole et al 1992): specifically, the motor and retrosplenial cortices innervate the lateral and medial striatum, respectively, whereas the PFC innervates the NAS (Ebrahimi et al 1992;Sesack et al 1989;van Groen andWyss 1992, 2003). Using functional connectivity analyses (Schwarz et al, 2007a, b), we characterized the regional correlation patterns in response amplitude to VU0152100.…”

Rat brains also have a default mode network

“…RSC is connected primarily to the rostrodorsal hippocampal formation, whereas caudal parts of the RSC are connected with caudoventral areas of the hippocampal formation. The elaborate connections between the RSC and the hippocampal formation suggest that this projection provides an important pathway by which the hippocampus affects learning, memory, and emotional behavior (42).…”

Evidence for a hypothalamothalamocortical circuit mediating pheromonal influences on eye and head movements.

“…Inputs to area 23 from the mediodorsal thalamic nucleus have also been described in the monkey, and we observed FG-labeled cells in this nucleus after RSPagl injections in the rat. More medial parts of the RSP receive denser inputs from LD as compared to LP and from different nuclei of the anterior thalamic group related to the mammillary body (20,21); inputs from the mediodorsal nucleus have not been described in the rat (17,21).…”