The claustrum enhances neural variability by modulating the responsiveness of the prefrontal cortex.

The claustrum is a densely interconnected structure involved in cognitive functions, but its influence on prefrontal circuits remains unclear. We conducted two-photon calcium imaging to assess mice dorsal prefrontal cortex (dPFC) cell responses during exposure to visual stimuli and widefield photostimulation of claustrum axons embedded in the dPFC. We identified three distinct subpopulations of neurons - sensory responsive, opto responsive, and opto-boosted cells-each exhibiting unique response dynamics to combined visual and optogenetic stimuli. Our findings reveal that claustrum stimulation increased single-cell variability while aligning average responses across neurons, thereby enhancing network homogeneity. During Pavlovian training, enhanced variability persisted, but homogeneity increased further, suggesting experience-dependent refinement. Finally, we performed claustrum axon silencing experiments which revealed that the claustrum may operate bidirectionally to maintain enhanced variability and homogeneity in the dPFC. These results highlight the crucial role of the claustrum in dynamically modulating dPFC activity, impacting both neuronal variability and network synchronization.