Abstract
Retrosplenial cortex (RSC) is a dorsomedial parietal area involved in a range of cognitive functions, including episodic memory, navigation, and spatial memory. Anatomically, the RSC receives inputs from dorsal hippocampal networks and in turn projects to medial neocortical areas. A particularly prominent projection extends rostrally to the posterior secondary motor cortex (M2), suggesting a functional corticocortical link from the RSC to M2 and thus a bridge between hippocampal and neocortical networks involved in mnemonic and sensorimotor aspects of navigation. We investigated the cellular connectivity in this RSC→M2 projection in the mouse using optogenetic photostimulation, retrograde labeling, and electrophysiology. Axons from RSC formed monosynaptic excitatory connections ontoM2pyramidal neurons across layers and projection classes, including corticocortical/intratelencephalic neurons (reciprocally and callosally projecting) in layers 2– 6, pyramidal tract neurons (corticocollicular, corticopontine) in layer 5B, and, to a lesser extent, corticothalamic neurons in layer 6. In addition to these direct connections, disynaptic connections were made via posterior parietal cortex (RSC→PPC→M2) and anteromedial thalamus (RSC→AM→M2). In the reverse direction, axons from M2 monosynaptically excited M2-projecting corticocortical neurons in the RSC, especially in the superficial layers of the dysgranular region. These findings establish an excitatory RSC→M2 corticocortical circuit that engages diverse types of excitatory projection neurons in the downstream area, suggesting a basis for direct communication from dorsal hippocampal networks involved in spatial memory and navigation to neocortical networks involved in diverse aspects of sensorimotor integration and motor control.
Original language | English (US) |
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Pages (from-to) | 9365-9374 |
Number of pages | 10 |
Journal | Journal of Neuroscience |
Volume | 36 |
Issue number | 36 |
DOIs | |
State | Published - Sep 7 2016 |
Funding
This work was supported by the National Institute of Neurological Disorders and Stroke–National Institutes of Health (Grant NS061963) and the National Institute of Mental Health–National Institutes of Health (Grant MH108837). We thank K. Guo and B. Suter for advice and suggestions and C. Maguire for technical assistance.
Keywords
- Circuit
- Motor
- Neocortex
- Optogenetic
- Retrosplenial
ASJC Scopus subject areas
- General Neuroscience