Acetylcholine dynamics in the retrosplenial cortex during spatial uncertainty

Adaptive behaviour requires updating internal models in response to uncertainty, which can be divided into expected and unexpected forms. The retrosplenial cortex (RSC) is a hub for spatial navigation and the default mode network, integrating egocentric and allocentric inputs, contextual information, and multiple spatial hypotheses. This positions the RSC as a key region for investigating how the brain represents uncertainty. Computational theories propose that acetylcholine (ACh) signals expected uncertainty, while noradrenaline signals unexpected uncertainty, but recent work suggests ACh may encode both prediction error and expected variance. How ACh contributes to uncertainty signalling in the dysgranular RSC (dRSC) remains largely unexplored. Using a head-fixed mouse virtual reality paradigm, I manipulated spatial uncertainty while monitoring ACh dynamics with GRAB-ACh3.5 and neuronal activity with two-photon calcium imaging in the dysgranular RSC (dRSC). Mice learned to anticipate reward in stable environments and adapted flexibly to changes in reward location or environmental context. GRAB-ACh imaging revealed that dRSC cholinergic dynamics are strongly modulated by uncertainty. Novel environment switches evoked large, sustained increases in ACh that diminished with repeated exposure, consistent with novelty signalling. Reward relocations produced smaller, phasic responses. Increasing expected uncertainty generated a gradual tonic rise in ACh, mirrored by pupil dilation. Critically, unexpected change under high expected uncertainty elicited both a strong phasic peak and a sustained ACh response, suggesting multiplexed coding of prediction error and expected variance. Two-photon imaging showed that dRSC neurons maintain stable positional maps but reorganise in response to uncertainty: global remapping after environment switches, partial reorganisation after reward shifts, and broadened activity fields under expected uncertainty. Muscarinic blockade disrupted positional coding in novel environments, directly linking ACh signalling to spatial representation dynamics. Together, these findings identify ACh in dRSC as a key modulator of adaptation to uncertainty, balancing stability and reorganisation of spatial and reward codes.<p></p>

Author dc:creator

• Dan Goodwin (21041336)

• Acetylcholine
• Retrosplenial cortex
• Uncertainty
• Position cells
• Virtual reality
• Two-photon microscopy

Statement dc:rights

• All rights reserved
• Open Access after 2027-03-10

Identifier

10779/exe.31626067.v1

OAI identifier oai:identifier

oai:figshare.com:article/31626067