Can’t remember where you keep things? Seem to forget names and appointments more often than before? Don’t blame your failing memory on age. It is more likely that you are not getting your quota of beauty sleep.

In an age of distractions (read: smartphone, social media, and TV) and trying to get too many things done in too little time, we often forego sleep. The result is not just dark circles under the eyes or yawning our heads off the next day in office. We also tend to forget more the less we sleep. Yes, scientists have cracked one more sleep code; sleep helps us form and cement long-term memories.

What does sleep do to our brains?

We don’t need to be told about the restorative effects of sleep because we wake up feeling rested and refreshed after a good night’s sleep. Psychological studies have always hinted that sleep helps form and cement memories by preventing mental and behavioral activities from interfering during the consolidation process. But now for the first time, scientists have decoded what happens inside our brains, at the synaptic level, when we sleep.

According to a recent report, sleep stimulates the brain cells to respond in two different ways. The synaptic connections either get strengthened, which facilitates long-term retention of memories, or get weakened, which leads to forgetting. The process of strengthening the memory is known as long-term potentiation (LTP) or consolidation. Scientists have identified a specific phosphorylated protein that influences LTP.

This study builds upon and bolsters a series of earlier studies carried out to determine the relationship between sleep and memory formation and consolidation.

According to another study, enduring memory formation is facilitated by rehearsing previously-learned matter. Much of this rehearsal takes place without us knowing it, which is when we sleep.

Some other studies hint at the role of dopamine in forming and consolidating memories and how sleep affects dopaminergic activity. A decrease in dopaminergic signaling improves the memory retention and consolidation process while an increase accelerates forgetting. These findings are in line with what scientists had discovered in earlier studies: there is less external and internal stimulation to activate dopamine neurons when a person is asleep, so there is less dopaminergic activity during sleep.

Sleep, memory and learning

Memory retention, consolidation, and retrieval are integral processes without which learning cannot take place. The findings from the earlier-mentioned studies make us curious about the implications of sleep on the learning process. Or as students would be curious to know—should I stay up late and cram for tomorrow’s exams or go to sleep?

According to a study carried out on laboratory mice, learning triggers the growth of spines on different dendritic branches. These spines correspond to new neuronal connections that form in response to learning new tasks. In the laboratory, two groups of mice were made to learn how to run on a spinning rod. Then one group of mice slept for 7 hours while the other group remained awake. After waking up, it was found that the mice that had slept had more dendritic spine growth than the animals that did not sleep.

Sleep and memory reorganization

Sleep not only consolidates memory and aids learning. It also reorganizes memories and reconfigures details that promote creativity. Qualitative reorganization of memories leads to the formation of new memories or associations that the subjects have not learned previously. This leads to creative and unique insights into a situation.

Sleep and false memory formation

There are several aspects of memory. Learning is considered effective not only when we retain what we have learned but also when we can reproduce or recall the learning matter accurately after a certain period of time. Memory may sometimes play tricks on us by distorting memories. This means that we sometimes “remember” events and experiences that have never occurred. Scientists have discovered a link between sleep and false memory formation.

According to one study, some types of memories degenerate over time and in response to sleep and lead to the formation of false memories. In this study, the subjects were made to study lists of words with similar semantic associations, like door, ledge, sill, curtain, house, shade, and so on. After a gap of two days, they were tested on their memory of the words. When prompted with cues, they also “remembered” a critical word that was not included in the original list. What is more, this false memory persisted the longer the gap was between memory formation and recall.

This indicates that sleep affects different types of memories differently. The difference stems from the specific location in the brain where a particular memory is processed.

Memories that are processed by the hippocampal region are consolidated more effectively after a period of deep sleep. But memory consolidation that requires semantic processing, as when we have to remember related words, takes place in the left ventrolateral prefrontal cortex and the left lateral temporal cortex. So, not all memories are improved by sleep.

Implications of the sleep-memory studies

We live in busy times where we are stretched too thin and get pulled in all directions. The first casualty is sleep. Everyone should take note of the findings from the above-mentioned studies. It is evident that sleep improves learning by helping consolidate memories.

So students should not push themselves to forego sleep to study till the wee hours. Educators and teachers should organize the curriculum such that students do not feel burdened by the amount of material they have to study. Curriculum developers may also consider revamping the pattern of assessments so that these test the analytical abilities of the students rather than their capacity for rote learning.

Professionals should minimize distractions and organize their lives so that they are not compelled to stay up late to prepare presentations or learn new concepts and skills relevant to their jobs.

The studies on the relation between sleep and memory provide critical insights into how to make the learning process more effective. Do not skimp on the shut-eye!

References

Berry, J., Cervantes-Sandoval, I., Nicholas, E., & Davis, R. (2012). Dopamine Is Required for Learning and Forgetting in Drosophila Neuron, 74 (3), 530-542 DOI: 10.1016/j.neuron.2012.04.007

Berry, J., Cervantes-Sandoval, I., Chakraborty, M., & Davis, R. (2015). Sleep Facilitates Memory by Blocking Dopamine Neuron-Mediated Forgetting Cell, 161 (7), 1656-1667 DOI: 10.1016/j.cell.2015.05.027

Blanco, W., Pereira, C., Cota, V., Souza, A., Rennó-Costa, C., Santos, S., Dias, G., Guerreiro, A., Tort, A., Neto, A., & Ribeiro, S. (2015). Synaptic Homeostasis and Restructuring across the Sleep-Wake Cycle PLOS Computational Biology, 11 (5) DOI: 10.1371/journal.pcbi.1004241

Landmann, N., Kuhn, M., Piosczyk, H., Feige, B., Baglioni, C., Spiegelhalder, K., Frase, L., Riemann, D., Sterr, A., & Nissen, C. (2014). The reorganisation of memory during sleep Sleep Medicine Reviews, 18 (6), 531-541 DOI: 10.1016/j.smrv.2014.03.005

Oudiette, D., Antony, J., Creery, J., & Paller, K. (2013). The Role of Memory Reactivation during Wakefulness and Sleep in Determining Which Memories Endure Journal of Neuroscience, 33 (15), 6672-6678 DOI: 10.1523/JNEUROSCI.5497-12.2013

Payne, J., Schacter, D., Propper, R., Huang, L., Wamsley, E., Tucker, M., Walker, M., & Stickgold, R. (2009). The role of sleep in false memory formation Neurobiology of Learning and Memory, 92 (3), 327-334 DOI: 10.1016/j.nlm.2009.03.007

Yang, G., Lai, C., Cichon, J., Ma, L., Li, W., & Gan, W. (2014). Sleep promotes branch-specific formation of dendritic spines after learning Science, 344 (6188), 1173-1178 DOI: 10.1126/science.1249098

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