Sleep deprivation impairs ventral hippocampus-medial prefrontal connectivity and task learning in rats.

Sleep is essential for memory consolidation, and sleep loss has long been associated with cognitive impairment. However, the circuit-level mechanisms through which sleep deprivation disrupts hippocampal-prefrontal communication during learning remain poorly understood. Here, we combined a T-maze learning task with simultaneous local field potential (LFP) recordings in the ventral hippocampus (vHPC) and medial prefrontal cortex (mPFC) of rats. Using dynamic causal modeling (DCM), we quantified directional connectivity during task acquisition under normal and sleep-deprived conditions. We found that learning strengthened forward connectivity from vHPC to mPFC while weakening backward connectivity from mPFC to vHPC. Sleep deprivation impaired this forward connectivity, resulting in slower learning and reduced task accuracy. These findings characterize the altered circuit dynamics by which sleep loss disrupts hippocampal-prefrontal circuit dynamics, providing insight into how impaired cross-regional communication may underlie cognitive deficits observed in sleep-related psychiatric and neurodegenerative disorders.