Episode 3: Gina Poe - How sleep restructures our memories and emotions

Sep 15, 2020

Gina Poe, UCLA neuroscientist who studies sleep, memory and emotion in rodents. She discusses memory replay during REM and how spindles time schema updating. She explores REM’s role in loosening and reconsolidating memories, links to PTSD and propranolol timing, and surprising local sleep where hippocampus and cortex dissociate.

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INSIGHT

Theta In REM Decides Strengthen Or Weaken

REM sleep shows constant hippocampal theta which can time strengthening or weakening of synapses.
Gina Poe found hippocampal cells fire at theta peaks for potentiation and at troughs for depotentiation, explaining REM's dual role.

INSIGHT

Replay Rehearses Memories In Different Speeds

Memory replay recreates neural sequences from wake during sleep and can occur in different speeds depending on sleep stage.
Matt Wilson and Bruce McNaughton showed fast-forward replay in slow sleep and real-time replay in REM, linking replay to rehearsal without external input.

INSIGHT

REM Enables Schema Updating By Turning Neuromodulators Off

REM uniquely permits weakening of existing cortical schemas because key neuromodulators are off.
Poe argues norepinephrine and serotonin absence in REM lets depotentiation occur so schemas can be loosened to incorporate new information.

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In this episode we ask Gina Poe, a sleep scientist from UCLA, about her seminal work on both REM and non-REM sleep. We talk about the role of memory replay in REM, how to measure such replay in rats, as well as the ways in which REM impacts upon emotional representations, and may even help us to combat post traumatic stress disorder (PTSD). We also discuss the importance of sleep spindles for updating conceptual knowledge. Finally, we describe Professor Poe's ground-breaking findings on local sleep and how these may change the face of sleep research in the future.

Produced by: Eniko Simo

See Professor Poe's faculty profile:
https://www.ibp.ucla.edu/faculty/gina-poe/

Find the research papers mentioned in this episode here:
https://academic.oup.com/sleep/article/39/12/2201/2706367
https://www.sciencedirect.com/science/article/pii/S096098221831279X?via%3Dihub
https://link.springer.com/article/10.1007/s00221-014-3890-4
https://www.liebertpub.com/doi/10.1089/jwh.2020.8332

Glossary:
EEG = Electroencephalography is an electrophysiological monitoring method for non-invasively recording the electrical activity of the brain via electrodes placed on the scalp.

Heterosynaptic plasticity = when synaptic pathways that were not directly stimulated themselves undergo changes (synaptic plasticity) as a result of neighbouring synapses being stimulated. Often this means that as one pathway is used and strengthened, an unused neighbouring pathway gets weakened.

PTSD = Post-traumatic stress disorder is a mental health condition that's triggered by a terrifying event. Symptoms may include flashbacks, nightmares, and severe anxiety, as well as uncontrollable thoughts about the event.

Schema = a cognitive framework or concept that helps organize and interpret information.

Spindle = distinct brain waves with frequency 11-16 Hz (measured with EEG).

Theta = 4-8 Hz brainwave frequencies.

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