REM

Rapid eye movement sleep is marked by theta rhythm, increased cholinergic tone, and muscle paralysis with the exception of eye muscles.

## Description

* Higher theta frequency as measured by EEG or LFP (all of cortex or certain areas?)
* Associated with dreaming — dreams are more likely to be remembered when awoken during REM sleep
* Kids spend ~50% of sleep in REM, while adults spend more ~20%, however this goes up after learning.
* One study attenuated IP3-mediated Calcium signaling in astrocytes and looked at sleep architecture.
	+ Mice spent more time in REM sleep, entered the state more frequently, and had increased theta frequency power.
	+ Effect size not that impressive
* Optic activation of cholinergic neurons in pons increases REM sleep.
* NMDAR-dependent dendritic Calcium spikes occur at a high frequency during REM sleep.

## Function

* Evidence suggests that REM sleep does not play as big a role in procedural memory consolidation as NREM sleep.
* REM sleep deprivation (REMD) during development produces deficits in visual system and behavioral changes in adulthood.
* Loss of REM sleep in humans due to brainstem lesions has no gross impact on cognition.
* It's proposed that REM sleep might have a specific role in synaptic plasticity and pruning. The preponderance of REM sleep during early development when plasticity and pruning are more prominent and that novel experiences increase expression of synaptic plasticity genes during REM sleep support this.
	+ counter evidence: 8 hour REMD has no effect on motor-learning-induced dendritic spines in L5 motor cortex
	+ REMD leads to a greater elimination of newly formed spines
	+ REM sleep might increase pruning of new synapses/spines in the short term (0-16h) while maintaining and increasing the size of a fraction of synapses especially associated with motor learning in L5 Motor Cortex.
	+ NMDAR-dependent dendritic Calcium spikes during REM might play a role in this pruning/selective strengthening.

## References

1. ↑ Smith, C. & Lapp, L. Increases in number of REMS and REM density in humans following an intensive learning period. Sleep 14, 325–330 (1991
2. ↑ http://journal.frontiersin.org/article/10.3389/fncir.2017.00003/full
3. ↑ Van Dort, C. J., Zachs, D. P., Kenny, J. D., Zheng, S., Goldblum, R. R., Gelwan, N. A., et al. (2015). Optogenetic activation of cholinergic neurons in the PPT or LDT induces REM sleep. *Proc. Natl. Acad. Sci. U.S.A.* 112, 584–589. doi: 10.1073/pnas.1423136112
4. ↑ 4.0 4.1 4.2 http://www.nature.com.resources.library.brandeis.edu/neuro/journal/v20/n3/full/nn.4479.html
5. ↑ Pharmacological REM sleep suppression paradoxically improves rather than impairs skill memory

Nat. Neurosci., 12 (2009), pp. 396–397
6. ↑ Marks, G.A., Shaffery, J.P., Oksenberg, A., Speciale, S.G. & Roffwarg, H.P. A functional role for REM sleep in brain maturation. Behav. Brain Res. 69, 1–11 (1995).
7. ↑ 7.0 7.1 http://www.nature.com.resources.library.brandeis.edu/neuro/journal/vaop/ncurrent/full/nn.4479.html#ref10
8. ↑ Vertes, R.P. & Siegel, J.M. Time for the sleep community to take a critical look at the purported role of sleep in memory processing. Sleep 28, 1228–1229, discussion 1230–1233 (2005).
9. ↑ Rasch, B. & Born, J. About sleep's role in memory. Physiol. Rev. 93, 681–766 (2013).