The Neuroscience of Sleep Deprivation and Memory
Sleep is a dynamic process involving complex neural activation, but it has become a natural part of every day of our lives. A common question is usually whether or not someone is getting enough sleep. From a neuroscience perspective, you can appreciate the importance of sleep. Sleep helps us function as human beings, allows us to learn new information and store memories, build new habits and achieve our potential as humans. Without sleep, our ability to problem-solve, speak, and think would be significantly damaged. With this in mind, sleep can become crucial in our lives.
The Neurobiology of Sleep
Sleep is a complex process essential for maintaining physical and mental health. During sleep, the brain undergoes several changes that help to restore and rejuvenate the body and mind.
When you fall asleep, your brain waves slow and become less synchronized. This is known as non-rapid eye movement (NREM) sleep. After about 90 minutes, your brain waves become more synchronized and rapid, known as rapid eye movement (REM) sleep.
During NREM sleep, the body’s systems slow down, and the brain is less active. This allows the body to repair itself and restore energy levels. Blood flow to the muscles increases, and the release of hormones that promote growth and development also increases.
During REM sleep, the brain becomes more active, and dreams occur. This is the stage of sleep when most of the brain’s processing and consolidation of memories occurs. The body becomes paralyzed, which prevents us from acting out our dreams.
Sleep is regulated by the circadian rhythm, controlled by a part of the brain called the suprachiasmatic nucleus (SCN). The SCN responds to light and dark signals to help regulate the body’s internal clock and determine when we feel awake and sleepy.
Sleep is also affected by several neurotransmitters, such as serotonin, dopamine, and GABA. These chemicals help to promote sleep and regulate the sleep-wake cycle.
Overall, the neuroscience of sleep is complex and involves many different processes in the brain. Getting enough sleep is essential for maintaining good physical and mental health.
This image is a great way to visualize sleep and the systems involved in the different sleep processes.
The Neurobiology of Memory
With a similar goal in mind of providing background on sleep, I will give comparable knowledge on the neurobiology of memory. Memory, which is the ability to retain information and recall it at a later time, is biologically fundamental for survival. As humans, memory shapes our identity by guiding our thoughts and decisions and influencing our emotional reactions.
Memory is a complex process that involves multiple areas of the brain. It consists of the encoding, storage, and retrieval of information.
When you first encounter a piece of information, it is processed by the hippocampus, a region of the brain involved in forming new memories. The hippocampus encodes the data into a form that can be stored in the brain.
Once encoded, the information is stored in various brain regions, such as the prefrontal cortex and the neocortex. The location where the data is stored depends on the type of memory. For example, memories of facts and concepts are typically stored in the neocortex, while the memory of skills is stored in the basal ganglia and the cerebellum.
When you need to retrieve a memory, the hippocampus retrieves it from its stored location and sends it back to the appropriate area of the brain for processing. This allows you to access the memory and use it in your thoughts and actions.
Many factors, such as age, stress, and certain medical conditions, can affect memory ability. For example, as we age, our ability to form new memories tends to decline, and people with conditions like Alzheimer’s disease often have difficulty with memory. However, there are also many ways to improve memory, such as regularly engaging in activities challenging the brain and practicing good sleep hygiene.
The Neuroscience of Sleep Deprivation
Sleep deprivation is a condition that occurs when a person does not get enough sleep. The effects of sleep deprivation can vary depending on the individual and the amount of sleep they are missing. Still, it can impair cognitive function, cause mood changes, and lead to physical health problems.
In neuroscience, sleep deprivation can affect the brain in several ways. It can impair the function of the prefrontal cortex, the part of the brain responsible for decision-making, problem-solving, and impulse control. This can lead to difficulty concentrating, poor judgment, and increased impulsivity.
Sleep deprivation can also alter the levels of neurotransmitters in the brain, such as dopamine and serotonin. These chemicals are involved in mood regulation, and changes in their levels can cause mood changes such as irritability, anxiety, and depression.
Additionally, sleep deprivation can affect the brain’s ability to consolidate memories. During sleep, the brain processes and consolidates information learned during the day, and without enough sleep, this process can be disrupted, leading to difficulty remembering new information.
Sleep deprivation can also affect the body’s ability to regulate its internal systems, such as body temperature and blood pressure. This can lead to physical health problems, such as an increased risk of heart disease and diabetes.
Overall, the effects of sleep deprivation on the brain and body can be significant. It is essential to get enough sleep to maintain good physical and mental health.
How sleep deprivation can affect you
- Impaired cognitive function, including difficulty concentrating and poor decision-making.
- Mood changes, such as irritability and anxiety.
- Increased risk of physical health problems, such as heart disease and diabetes.
- A weakened immune system makes it harder for the body to fight off illness.
- Weight gain, as sleep deprivation, can disrupt the body’s regulation of hunger hormones.
- Increased risk of accidents and injuries due to impaired cognitive and motor function.
Studies to look at to dive deeper into this topic
This study discussed how sleep deprivation reduces spine numbers and dendrite length in CA1 neurons of the hippocampus without affecting the dendritic structure of CA3 neurons. They also found that three hours of recovery sleep restores spine number, dendrite length, and cofilin phosphorylation levels in non-sleep-deprived mice. Sleep deprivation decreases the apical/basal dendrite length of CA1 neurons.
This image looks at the reward-relevant brain regions that are affected by sleep deprivation (SD), including cortical regions (blue) such as the medial prefrontal cortex (mPFC), insula and orbitofrontal cortex (OFC), and the subcortical region of the striatum (red). Increased adenosine load (blue circles) associated with SD triggers downregulation of dopamine (DA) D2 and D3 receptors (D2/3Rs), resulting in decreased receptor membrane expression within the striatum (internalized receptors; grey). Consequently, there is a more excellent ratio of D1R to D2/3R availability, and the relative increase in striatal D1R activation by DA (green circles) under SD conditions is proposed to increase risk-related and reward-related approach behaviors, shown in the see-saw imbalance. SD further disrupts incentive processing within PFC regions and thus is proposed to result in a lower signal-to-noise ratio (SNR) under SD conditions (represented by a narrow dynamic range of PFC sensitivity). This consequentially impairs the ability to accurately map and update changing value or reward probability (colored dots) over time — such as that involved in reinforcement learning, ultimately contributing to non-optimal incentive-based decision-making.
This image looks at sleep deprivation (SD) amplifies amygdala reactivity (red) in response to negative emotional stimuli and decreases associated amygdala–medial prefrontal cortex (mPFC) connectivity (blue). a.SD alters the sensitivity of the salience-detection network (the amygdala, anterior cingulate cortex (ACC), and anterior insula (AI)) to varying levels of emotional stimuli that range in valence strength (x-axis in the two graphs) from negative (red) to neutral (blue) to positive (red). Under sleep-rested conditions (left graph), there is a broad and dynamic range of salience-detection sensitivity, resulting in the ability to accurately discriminate between degrees of emotional salience (tall vertical difference arrow; discerning emotional (red vertical line) from neutral stimuli (blue vertical line)). By contrast, SD (right graph) is proposed to trigger a narrowing and, thus, a more nonspecific detection sensitivity range, impairing the ability to accurately discriminate between degrees of emotional salience (short vertical difference arrow). This loss of ‘net neutrality results in over-generalized emotional sensitivity, wherein an otherwise largely neutral stimulus (blue vertical line) is inappropriately registered as ‘emotional’ by the salience-detection network, further observed in biased emotional ratings of neutral stimuli. A downstream behavioral consequence of these significant brain changes, in combination with disrupted peripheral autonomic nervous system feedback of visceral body information, could lead to inaccurate and even absent outward expression of emotions. This is supported by experimental evidence demonstrating that individuals deprived of sleep fail to register emotional faces shown on a screen and, consequently, cannot accurately mimic the emotional facial expressions of these target faces.
References
- https://qbi.uq.edu.au/brain-basics/memory/where-are-memories-stored
- https://thebrain.mcgill.ca/flash/d/d_11/d_11_cr/d_11_cr_cyc/d_11_cr_cyc.html
- https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep
- Krause, A. J., Simon, E. B., Mander, B. A., Greer, S. M., Saletin, J. M., Goldstein-Piekarski, A. N., & Walker, M. P. (2017). The sleep-deprived human brain. Nature reviews. Neuroscience, 18(7), 404–418. https://doi.org/10.1038/nrn.2017.55
- https://factdr.com/mental-well-being/sleep-deprivation-harming-you/
- https://newsinhealth.nih.gov/2013/04/sleep-it
- Robbert Havekes, Alan J Park, Jennifer C Tudor, Vincent G Luczak, Rolf T Hansen, Sarah L Ferri, Vibeke M Bruinenberg, Shane G Poplawski, Jonathan P Day, Sara J Aton, Kasia Radwańska, Peter Meerlo, Miles D Houslay, George S Baillie, Ted Abel (2016) Sleep deprivation causes memory deficits by negatively impacting neuronal connectivity in hippocampal area CA1 eLife 5:e13424 https://doi.org/10.7554/eLife.13424
- https://www.sleepfoundation.org/how-sleep-works/memory-and-sleep
- Alhola, P., & Polo-Kantola, P. (2007). Sleep deprivation: Impact on cognitive performance. Neuropsychiatric disease and treatment, 3(5), 553–567.
- Cousins, J. N., & Fernández, G. (2019). The impact of sleep deprivation on declarative memory. Progress in brain research, 246, 27–53. https://doi.org/10.1016/bs.pbr.2019.01.007
- Lo, J. C., Chong, P. L., Ganesan, S., Leong, R. L., & Chee, M. W. (2016). Sleep deprivation increases the formation of false memory. Journal of sleep research, 25(6), 673–682. https://doi.org/10.1111/jsr.12436
- Vaseghi, S., Arjmandi-Rad, S., Kholghi, G., & Nasehi, M. (2021). Inconsistent effects of sleep deprivation on memory function. EXCLI journal, 20, 1011–1027. https://doi.org/10.17179/excli2021-3764
- Delorme, J., Wang, L., Kuhn, F. R., Kodoth, V., Ma, J., Martinez, J. D., Raven, F., Toth, B. A., Balendran, V., Vega Medina, A., Jiang, S., & Aton, S. J. (2021). Sleep loss drives acetylcholine- and somatostatin interneuron-mediated gating of hippocampal activity to inhibit memory consolidation. Proceedings of the National Academy of Sciences of the United States of America, 118(32), e2019318118. https://doi.org/10.1073/pnas.2019318118
- •Abel, T., Havekes, R., Saletin, J. M., & Walker, M. P. (2013). Sleep, plasticity, and memory from molecules to whole-brain networks. Current biology: CB, 23(17), R774–R788. https://doi.org/10.1016/j.cub.2013.07.025
- •Wadhwa, M., Prabhakar, A., Ray, K., Roy, K., Kumari, P., Jha, P. K., Kishore, K., Kumar, S., & Panjwani, U. (2017). Inhibiting the microglia activation improves spatial memory and adult neurogenesis in rat hippocampus during 48 h of sleep deprivation. Journal of neuroinflammation, 14(1), 222.
- •Gerhardsson, A., Åkerstedt, T., Axelsson, J., Fischer, H., Lekander, M., & Schwarz, J. (2019). Effect of sleep deprivation on emotional working memory. Journal of sleep research, 28(1), e12744. https://doi.org/10.1111/jsr.12744
- •Kim, S. M., Zhang, S., Park, J., Sung, H. J., Tran, T. T., Chung, C., & Han, I. O. (2021). REM Sleep Deprivation Impairs Learning and Memory by Decreasing Brain O-GlcNAc Cycling in Mouse. Neurotherapeutics: the journal of the American Society for Experimental NeuroTherapeutics, 18(4), 2504–2517. https://doi.org/10.1007/s13311-021-01094-7
