Role of Sleep in Memory

Eitan Schechtman’s talk on his research on targeted memory reactivation (TMR) mentioned how sleep may play a role in memory consolidation. Furthermore, he mentioned how we can enhance/induce memory consolidation through the use of sound and odor cues. The underlying mechanism of how this occurs is not very well known, but studies done on mice and humans suggest that hippocampal replay might be occurring during sleep. Hippocampal replay is the phenomenon where certain place cells that are active during the mice/human is performing a task are also reactivated during sleep. And due to these cues, which subjects were exposed to both during learning and sleep, we are able to target the reactivation of those memories associated with the cues. In his own research, Dr.Eitan used sound cues presented both during learning and sleep, and found that in the group that was exposed to sound cues during both learning and sleep performed better on the location task. Through TMR they were also able to target not only what the participants should remember, but also what they should forget. This talk emphasizes a critical role of sleep and provides a new method for combating PTSD and phobias.

Furthermore, according to an article from The New York Times titled “The Purpose of Sleep?
To Forget, Scientists Say” by Carl Zimmer, sleep may be important for forgetting. A negative connotation is associated with forgetting, however our brains do not have an unlimited amount of space, so it only makes sense that those unimportant memories are forgotten. Synaptic homeostasis hypothesis, proposed by researchers from the University of Wisconsin-Madison Giulio Tononi and Chiara Cirelli, proposes that during sleep a synaptic downscaling occurs where certain unimportant synapses are pruned away. The synaptic downscaling is a mechanism through which only strong memories remain while the weak/unimportant ones are pruned. Further evidence suggests that during sleep the protein Homer1A, which helps with the pruning process, increases in synapses. Additionally, when they injected a chemical that blocks pruning in mice, they become unable to discriminate between different contexts. In the experiment they used fear conditioning, where both the control and chemical injected mice were shocked in a chamber, after which both groups would freeze when placed in that chamber. After the mice were allowed to sleep, when they placed both mice groups in a different chamber they found that control mice freely explored the new environment, while the other group froze again. 

Both the talk and the article focus on the role of sleep, which is not very well understood currently. But sleep is considered to be very important not only for memory, but also for normal functioning. Sleep deprivation has been linked to almost “72,000 crashes, 44,000 injuries, and 800 deaths” just in 2013, as it leads to cognitive deficits (CDC, 2019). Further research on sleep is needed to know its role and how it impacts us not only in the short term but also long term.

                                                               Works Cited

CDC.“Drowsy Driving: Asleep at the Wheel.” Centers for Disease Control and Prevention, 

Centers for Disease Control and Prevention, 7 Nov. 2019, https://www.cdc.gov/features/dsdrowsydriving/index.html.

Schouten, Daphne I., et al. “State of the Art on Targeted Memory Reactivation: 

Sleep Your Way to Enhanced Cognition.” Sleep Medicine Reviews, vol. 32, 2017, pp. 123–131., doi:10.1016/j.smrv.2016.04.002.

Zimmer, Carl. “The Purpose of Sleep? To Forget, Scientists Say.” The New York Times, The New York Times, 2 Feb. 2017, https://www.nytimes.com/2017/02/02/science/sleep-memory-brain-forgetting.html.