Prefrontal coding of learned and inferred knowledge during REM and NREM sleep

Area of Science:

• Neuroscience
• Cognitive Science

Background:

• Idling brain activity is theorized to aid inference and problem-solving.
• The precise mechanisms and timing of novel idea generation during brain idling remain unclear.

Purpose of the Study:

• To investigate the necessity and sufficiency of cortical offline activity for forming unlearned inferential knowledge.
• To elucidate the distinct roles of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep in cognitive inference.

Main Methods:

• Transitive inference paradigm in male C57BL/6J mice.
• Inhibition of neuronal activity in the anterior cingulate cortex (ACC) during post-learning sleep and wakefulness.
• In vivo Ca2+ imaging to observe neural dynamics during sleep stages.
• Artificial activation of medial entorhinal cortex-ACC pathways during REM sleep.

Main Results:

• Inference was acquired 1 day post-training, not immediately after.
• Inhibiting ACC during NREM or REM sleep, but not wakefulness, impaired inference acquisition.
• NREM sleep appeared to organize learned information into a hierarchy, while REM sleep computed inferential knowledge from this hierarchy.
• Artificial REM sleep activation of the medial entorhinal cortex-ACC pathway facilitated inference even after insufficient learning.

Conclusions:

• Cortical offline activity during sleep is both necessary and sufficient for inferential knowledge acquisition.
• NREM and REM sleep exhibit a coordinated function, with NREM organizing information and REM computing novel inferences.
• This study provides mechanistic insights into how the idling brain contributes to cognitive flexibility and insight.