Infralimbic activity during REM sleep facilitates fear extinction memory.

Area of Science:

• Neuroscience
• Sleep Science
• Memory Research

Background:

• Rapid eye movement (REM) sleep is recognized for its role in processing fearful memories and facilitating fear extinction.
• Disruptions in REM sleep following trauma are linked to an increased risk of developing post-traumatic stress disorder (PTSD).
• The precise mechanisms through which REM sleep supports the extinction of aversive memories are not fully understood.

Purpose of the Study:

• To investigate the role of the infralimbic cortex (IL) during REM sleep in the consolidation of fear extinction memory.
• To elucidate the neural mechanisms underlying REM sleep's protective effects against traumatic memories.

Main Methods:

• Calcium imaging in mice to observe IL pyramidal neuron activity during REM sleep.
• Optogenetic manipulation to suppress IL activity specifically during REM sleep at different time points.
• Whole-cell patch-clamp recordings to assess neuronal excitability after REM sleep inhibition.

Main Results:

• Most IL pyramidal neurons show significant activation during REM sleep.
• Optogenetic suppression of the IL during REM sleep within 4 hours post-fear conditioning impaired extinction memory consolidation.
• REM-specific IL inhibition after extinction learning did not impact established extinction memory.
• Inhibiting IL neurons during REM sleep reduced their overall excitability.

Conclusions:

• REM sleep following fear conditioning enhances fear extinction by increasing IL neuronal excitability.
• These findings underscore the critical role of REM sleep in the immediate aftermath of traumatic events for mitigating the persistence of traumatic memories.
• Targeting REM sleep could offer novel therapeutic strategies for PTSD prevention.