Strategy-Specific Patterns of Arc Expression in the Retrosplenial Cortex and Hippocampus during T-Maze Learning in Rats

Abstract

The retrosplenial cortex (RSC) belongs to the spatial memory circuit, but the precise timeline of its involvement and the relation to hippocampal activation have not been sufficiently described. We trained rats in a modified version of the T maze with transparent walls and distant visual cues to induce the formation of allocentric spatial memory. We used two distinct salient contexts associated with opposite sequences of turns. Switching between contexts allowed us to test the ability of animals to utilize spatial information. We then applied a CatFISH approach with a probe directed against the Arc immediate early gene in order to visualize the associated memory engrams in the RSC and the hippocampus. After training, rats displayed two strategies to solve the maze, with half of the animals relying on distant spatial cues (allocentric) and the other half using egocentric strategy. Rats that did not utilize the spatial cues showed higher Arc levels in the RSC compared to the allocentric group. The overlap between the two context engrams in the RSC was similar in both groups. These results show differential involvement of the RSC and hippocampus during spatial memory acquisition and point toward their distinct roles in forming the cognitive maps.

Disrupting direct inputs from the dorsal subiculum to the granular retrosplenial cortex impairs flexible spatial memory in the rat

“…Findings from a very different type of behavioural task, contextual fear conditioning, also implicate both the hippocampus (including the dorsal subiculum) and retrosplenial cortex in learning about space (Anagnostaras et al, 2001; Keene & Bucci, 2008; de Melo et al, 2020; Miller et al, 2014; Pan et al, 2022; Smith et al, 2012). Meanwhile, immediate‐early gene analyses indicate that the two regions have complementary roles in spatial tasks (Czajkowski et al, 2020; Frankland & Bontempi, 2005). In addition, neuronal recordings suggest that the hippocampus may encode and help distinguish contexts, while the retrosplenial cortex may enable behaviourally significant cues to identify the current context (Smith et al, 2012) or help predict future navigational decisions (Miller et al, 2019).…”

Disrupting direct inputs from the dorsal subiculum to the granular retrosplenial cortex impairs spatial memory in the rat

“…Findings from a very different type of behavioural task, contextual fear conditioning, also implicate both the hippocampus (including the dorsal subiculum) and retrosplenial cortex in learning about space (Anagnostaras et al, 2001;Keene & Bucci, 2008;Melo et al, 2020;Miller et al, 2014;Pan et al, 2022;Smith et al, 2012). Meanwhile, immediate-early gene analyses indicate that the two regions have complementary roles in spatial tasks (Czajkowski et al, 2020;Frankland & Bontempi, 2005). In addition, neuronal recordings suggest that the hippocampus may encode and help distinguish contexts, while the retrosplenial cortex may enable behaviourally significant cues to identify the current context (Smith et al, 2012) or help predict future navigational decisions (Miller et al, 2019).…”

Two complementary circuits for spatial navigation in mouse: evidence from Fos mapping

“…We have also shown that a measurable behavioral output in a spatial exploration paradigm could be produced by a range of alternative brain networks. In a seemingly homogeneous population of animals, different spatial strategies might spontaneously emerge and develop [8]. In this paper we investigated the possibility of engaging a specific spatial memory circuit as a result of the training protocol used.…”