What is memory consolidation?
In the most simplest terms, memory consolidation is the process of converting a short term memory into a more stable, long-term memory. Memory formation typically occurs in three different stages: encoding, storage, and retrieval. Encoding is the sensory inputs that have to be transformed into storable memory inputs. Storage then is how that encoded information is then transferred to the sense organs and retained. Finally, retrieval is how one can get access to the actual memory stores in the brain when wanting to recover information. The biology of how conscious memory is stored is that it is dependent on storage in the hippocampus and neocortex. The information is first stored in the hippocampus, known for its fast-learning system. Next, it is trained in the slow learning system of the neocortex. Memory consolidation is strengthened through this process by potentiation-a process requiring conduction of information from neuron to neuron to create a strong synaptic workforce. The more signals that pass through the synapse from one to neuron to the next, the more potentiation is built.
However, how does sleep play a role in this potentiation? REM sleep. That is the key stage of sleep that seems to have the greatest impact in strengthening potentiation. REM sleep is known as active sleep, which elicits neuronal activity in the brain through neuronal plasticity. The promotion of neuronal activity during REM sleep can therefore help consolidate memories and information a person stored during the day.1
Environmental Impacts
Proper REM sleep is vital in making short term memories more long term. The network of information that the active neurons build during REM sleep can impact overall memory. One issue greatly disturbing this sleep is the environment that people live in. Those living in poverty or a dangerous neighborhood with high crime rates may experience more difficulties getting proper sleep in all stages of the cycle. Imagine living in a neighborhood with gangs venturing outside your door. Imagine living by train tracks with a train that speeds by every night. Perhaps you live in a city that never sleeps. These interruptions can disrupt a person’s sleep cycle, having negative implications on the ability of their neurons to strengthen that synaptic plasticity during REM sleep. A sleep environment should be a dark, cool, and quiet place; this is not necessarily easy for most of the population to check off before going to bed.2 There are over 648 million people in the world that live in extreme poverty, and even more that live in poor conditions comparable to that.3 That is a lot of people likely not getting the proper sleep due to their living conditions being in poor environments. Even cities with poorly insulated apartments can result in noises from neighbors that can disrupt sleep. The number of environmental reasons for sleep disruption is unbelievable.
Conclusion
Sleep is so important in the development of synaptic plasticity and memory consolidation through potentiation. While of course awake repetition of the learned information to transition the short term memory into a long one is important as well, sleep is a push towards really solidifying that memory without actively studying. In a sense, it almost feels like magic in how the mind works to build stronger neuron connections while we peacefully sleep. Of course, peaceful sleep is not a privilege everyone has and is a difficult issue to solve because of all the different factors contributing to the disruption.
Citations:
- Memory consolidation. (2020, August 28). Ian. https://human-memory.net/memory-consolidation/#Basics_of_Memory_Consolidation
- Creating a good sleep environment. (2021, June 29). CDC. https://www.cdc.gov/niosh/emres/longhourstraining/environment.html
- Schoch, M., Baah, S. K. T., Lakner, C., & Friedman, J. (n.d.). Half of the global population lives on less than US$6.85 per person per day. World Bank Blogs. Retrieved March 28, 2023, from https://blogs.worldbank.org/developmenttalk/half-global-population-lives-less-us685-person-day
- Feld, G. B., & Diekelmann, S. (2020). Building the Bridge: Outlining steps toward an applied sleep-and-memory research program. Current Directions in Psychological Science, 29(6), 554–562. https://doi.org/10.1177/0963721420964171
