DOPAMINERGIC MODULATION OF SELECTION AND REACTIVATION OF HIPPOCAMPAL SPATIAL REPRESENTATIONS

Memory reactivation during sleep is thought to play a crucial role in the consolidation of episodic memories, yet it remains unclear which experiences are selected for reactivation and by what mechanisms.

In the hippocampus, behaviorally relevant place cell sequences are preferentially replayed during sharp-wave ripples, contributing to the stabilization of spatial representations. Notably, place cells reorganize their spatial selectivity in response to changes in reward contingencies, and newly remapped ensembles are selectively incorporated into replay events. While dopamine has been implicated in reward-dependent remapping and replay, how endogenous dopamine release relates to the selection and reactivation of spatial representations remains unresolved.

Here, we combine genetically encoded dopamine sensors with high-density electrophysiology to examine how dopaminergic modulation of the dorsal hippocampus shapes place cell remapping and replay during spatial reward learning. Toward this, we implemented a head-fixed treadmill task, in which mice learn space-reward associations while the reward location is systematically shifted across sessions to induce novel learning and repeated remapping. Continuous fiber photometry provides a temporally resolved measure of dopamine dynamics, while Neuropixels recording enables the monitoring of large-scale neuronal ensembles and network dynamics across hippocampal subregions.

We test whether dopamine signals during active navigation predict the selective recruitment of newly-learned reward-related trajectories into reverse replay during subsequent rest, and whether this relationship evolves across repeated learning experiences as environments transition from novel to familiar. By linking endogenous dopamine release to hippocampal ensemble dynamics, this work aims to elucidate how neuromodulation prioritises behaviourally relevant spatial memories for consolidation.