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Evidence for two distinct thalamocortical circuits in retrosplenial cortex

Lomi, E; Mathiasen, ML; Yin Cheng, H; Zhang, N; Aggleton, JP; Mitchell, AS; Jeffery, KJ; (2021) Evidence for two distinct thalamocortical circuits in retrosplenial cortex. Neurobiology of Learning and Memory , 185 , Article 107525. 10.1016/j.nlm.2021.107525. Green open access

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Abstract

Retrosplenial cortex (RSC) lies at the interface between sensory and cognitive networks in the brain and mediates between these, although it is not yet known how. It has two distinct subregions, granular (gRSC) and dysgranular (dRSC). The present study investigated how these subregions differ with respect to their electrophysiology and thalamic connectivity, as a step towards understanding their functions. The gRSC is more closely connected to the hippocampal formation, in which theta-band local field potential oscillations are prominent. We, therefore, compared theta-rhythmic single-unit activity between the two RSC subregions and found, mostly in gRSC, a subpopulation of non-directional cells with spiking activity strongly entrained by theta oscillations, suggesting a stronger coupling of gRSC to the hippocampal system. We then used retrograde tracers to test for differential inputs to RSC from the anteroventral thalamus (AV). We found that gRSC and dRSC differ in their afferents from two AV subfields: dorsomedial (AVDM) and ventrolateral (AVVL). Specifically: (1) as a whole AV projects more strongly to gRSC; (2) AVVL targets both gRSC and dRSC, while AVDM provides a selective projection to gRSC, (3) the gRSC projection is layer-specific: AVDM targets specifically gRSC superficial layers. These same AV projections are topographically organized with ventral AV neurons innervating rostral RSC and dorsal AV neurons innervating caudal RSC. These combined results suggest the existence of two distinct but interacting RSC subcircuits: one connecting AVDM to gRSC that may comprise part of the cognitive hippocampal system, and the other connecting AVVL to both RSC regions that may link hippocampal and perceptual regions. We suggest that these subcircuits are distinct to allow for differential weighting during integration of converging sensory and cognitive computations: an integration that may take place in thalamus, RSC, or both.

Type: Article
Title: Evidence for two distinct thalamocortical circuits in retrosplenial cortex
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.nlm.2021.107525
Publisher version: https://doi.org/10.1016/j.nlm.2021.107525
Language: English
Additional information: © 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: Retrosplenial cortex, anterior thalamus, chronic rodent electrophysiology, head direction cells, neuroanatomy, spatial memory, theta-modulation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences > Experimental Psychology
URI: https://discovery.ucl.ac.uk/id/eprint/10135696
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