Proper functioning of the human brain and body heavily relies on quality sleep. The cycle between rapid eye movement sleep (REMS) and non-rapid eye movement sleep (NREMS) is especially essential for memory consolidation, the connection of neural networks, and general brain cleansing. In the article titled Developmental emergence of sleep rhythms enables long-term memory capabilities in Drosophila, Dr. Cavanaugh et al. show the effect of deep sleep in Drosophila (fruit flies) on long-term memory consolidation. Similarly, in Remembering to Forget: A Dual Role for Sleep Oscillations in Memory Consolidation and Forgetting, Dr. Langille illustrates that sleep rhythms and the oscillations of brain waves play a role in storing vital memories, and thus forgetting inessential information.
In the experiment conducted by Dr. Cavanaugh et al., the sleep patterns of fruit flies at different stages of development were observed. They determined that 3rd instar larvae (L3) experience deep bouts of sleep for consecutive lengths of time while 2nd instar larvae (L2) cycle through shorter, not-deep bouts of sleep. The inconsistent sleeping patterns of L2 indicate that larvae at this stage of development have not yet established a fully functioning circadian rhythm and do not yet have the capacity to experience deep sleep. The flies are then put through odor-quinine training cycles to assess long-term memory. Without a distinct circadian rhythm or deep sleep, L2 were unable to store long-term memories. These results further demonstrate that long-term memory consolidation is dependent on deep sleep and consistent circadian rhythm.
Dr. Langille also sought to determine the relationship between sleep and memory by investigating the oscillations of brain waves in REM and NREM sleep. She explains in her article that oscillations in NREMS are essential for synaptic plasticity. These oscillations in NREMS are associated with the strengthening of synaptic pathways, which ultimately leads to the encoding of information, and thus storage of long-term memories. She also outlines that changes in ionic composition of extracellular regions of the brain determine different stages in a circadian rhythm. Because oscillations in the brain are reliant on ionic charge throughout neurons, different sleep stages produce different oscillations. NREMS occurs during a period of sleep of low membrane excitability; therefore, potentiation of synaptic plasticity does not occur but strengthening of synaptic pathways does occur. Wakefulness as well as REMS are associated with an environment that is more suited for potentiating synaptic plasticity. Nevertheless, NREMS, REMS, and wakefulness are important in the creation and encoding of new memories.
The same waves that are essential in the storing of new memories are also involved in the neurobiological process of forgetting information. Neuronal pathways that are created during the formation of memory are disassembled by the same brain oscillations during forgetting. Forgetting is a necessary component of memory consolidation: the transfer of memories from the hippocampus to cortical areas of the brain allow for new hippocampal space and the elimination of useless information.
Both Cavanaugh et al. and Langille’s studies demonstrate the importance of healthy sleeping routines on the ability to store memories. Their results indicate that sleep is a basic human necessity, and individuals in society should place more priority in their sleep in order to ensure proper cognitive function.
References:
Amy R. Poe et al. (2023). Developmental emergence of sleep rhythms enables long-term memory in Drosophila. Sci. Adv. 9. DOI:10.1126/sciadv.adh2301
Langille J. J. (2019). Remembering to Forget: A Dual Role for Sleep Oscillations in Memory Consolidation and Forgetting. Frontiers in cellular neuroscience, 13, 71. https://doi.org/10.3389/fncel.2019.00071
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