Memory reactivation in rat medial prefrontal cortex happens dominantly in a sub-state of cortical up state during slow wave sleep

Abstract

Sleep has been conjectured to play an essential role in memory consolidation. The interaction between the cortex and the hippocampus is believed to be crucial in consolidation of episodic memory during slow-wave sleep. Here, I analyzed the neural activity of medial prefrontal cortex of rats that ran the sequence-memory task. Applying a three-state hidden Markov model revealed that UP-DOWN oscillation can be divided into DOWN states and two UP subtypes. DOWN states were separated from UP states by low firing rates and the two UP subtypes were distinguished by the differences in the decaying rate of population vector and the duration. Interestingly, the faster decorrelating sub-state contains memory reactivation predominantly. Next, by analyzing the hippocampal local field potentials in relation to the UP sub-states, we found that the power of sharp-wave ripples was stronger during the reactivating UP sub-state. Our results provide further support to the theory of memory consolidation.