The attitudes towards sleep has changed dramatically in the last couple of centuries. About 400 hundred years ago, famous playwrights like William Shakespeare would wax poetically about how wonderful sleep is. In the 20th century, the changing idea that sleep is a waste of time may be due in part to the invention of the light bulb. This does not change the fact that sleep is an important part of our biology. The brain works even when we are asleep, and some areas are even more active at this time. No one area controls sleep. The hypothalamus houses our biological clock, which indicates to the body when is a good time to be awake and to be asleep. This structure interacts within the hypothalamus, the lateral hypothalamus, and the ventrolateral preoptic nuclei. All these structures send signals to the brain stem, which in turn sends signals to the cortex. This releases neurotransmitters that tell us to stay awake. Sleep is a complicated phenomenon that involves many different structures (Foster, 2013).
Three ideas that Dr. Foster focuses on why we sleep are restoration, energy conservation, and brain processing and memory consolidation. The restoration idea is based on the theory that we need sleep to restore, replace, and rebuild components of our bodies that we use during the day. There are also genes that are involved in restoration and metabolic pathway, which only turn on when we are asleep. There is decent evidence to support this. The energy conservation idea is based on the idea that we sleep to save calories, but there isn’t enough evidence to support this. The last idea, brain processing and memory consolidation has a lot of evidence to support it. There are three advantages to sleep: enhances creativity, important neural connections are linked and strengthened, and less important neural connections fade away. On the flip-side when a person is sleep-deprived, the ability to learn new tasks is very difficult. Being tired and lacking sleep leads to having poor memory, poor creativity, increased impulsiveness and overall poor judgment (Foster, 2013).
When in a sleep-deprived, brain craves substances that are unhealthy for us when used irresponsible, like stimulants and alcohol. Caffeine and nicotine are the most common used stimulants, and the effect they have is wiring people. To combat this, many people turn to alcohol because it’s a sedative. Unfortunately, it only mimics sleep and long-term use harms some neural processing during memory consolidation and memory recall. These stances can be highly additive as well. Other health concerns are weight gain and sustained stress. Sustained stress can lead to loss of memory, suppressed immunity, and increases the risk of diabetes and cardiovascular disease (Foster, 2013).
There is are possible relations that sleep disruption has with mental illness. It’s be recorded in the past that severe mental illness and sleep disruption go hand in hand, but it’s been largely ignored until recently. Many groups today are studying depression, schizophrenia, and bipolar in relation to sleep. He talks about a big study published on sleep and schizophrenia. It found that the many participates with schizophrenia were awake at night and asleep during the day. Others with schizophrenia had no ability to regulate sleep by light-dark cycle. Within the brain mental illness and sleep seem to have a mechanical link. There is evidence of overlapping neural networks between mental health and sleep. Also, mutated genes that are important for sleep may predispose individuals to mental health problems. This can lead to new understanding how both sleep and mental illness are generated and regulated in the brain. It also shows that sleep disruption may be an early warning signal of mental illness and can lead early intervention. Lastly this possible relation between sleep and mental illness may be a new therapeutic target (Foster, 2013).
The concepts from this talk that I will be focusing on are the relations between sleep, schizophrenia, and memory consolidation.
Sleep deprivation impacts a lot of mental processes. Tripthi et al. (2016) sets out to study the effects of short-term sleep deprivation has soon after training that may memory consolidation. The method used by the researchers was taking rats and dividing them into three groups. The first group was the sleep-deprived (SD) group, the second group was the nonsleep deprived (NSD) group, and the last was the stress control (SC) group. All the rats were trained for a delay-conditioning task with a house-light as the conditioned stimulus and fruit juice as the unconditioned stimulus. The SD group were gently disturbed for six hours after training, then were returned to the animal colony and allowed to rest undisturbed for a few hours. The NSD group were immediately returned to animal colony and not disturbed. The SC group were kept in a separate small enclosure and left there for six hours after training. After the six hours, they brought back to the colony. The results of Tripthi et al. (2016) were that the SD group performed significantly worse than the other groups after training and testing. The conclusion that the researchers drew was that the consolidation of delay-conditioned memory is sleep-dependent, and that REM sleep is also required for this process.
There is also a lot of interest in how memory loss is related to schizophrenia in conjunction with sleep. Wamsley et al. (2011) hypothesized that reductions of sleep spindles and sleep-dependent memory consolidation in patients with schizophrenia may be related. They’re method was to study two groups, the first consisted of chronic, medicated schizophrenia outpatients and the another of healthy volunteers. All participants were observed with a polysomnography for two consecutive nights. The first night of observation was to get a baseline of all the participants. On the second night, Wamsley et al. (2011) trained the participants in a finger tapping Motor Sequence Task (MST) right before bedtime. All the participants were tested the next morning and multiple variables were measured on performance. The results were that the schizophrenic outpatients failed to show improvement of MST and was significantly different from the results of the controls. Wamsley et al. (2011) suggests in their findings that abnormal sleep spindle generation negative effects sleep-dependent memory consolidation. Also that this may contribute to psychotic symptoms of schizophrenia and might be a potential target for treatment.
Sleep is huge part of our lives and one of its most important function is memory consolidation. Memory consolidation in turn is an important part of learning as a whole. Because there is no one structure in the brain the deals with sleep or memory and that there are many structures that assist with sleep and memory, there is potential for quite a bit of overlap between the two. We’ve also seen that there is no one section of the brain that is affected by mental illness, rather it affects the brain as a whole while being more concentrated in some parts than others. For example, schizophrenia takes a toll on the temporal lobe of the brain. One could argue that the temporal lobe becomes injured when the person becomes afflicted with schizophrenia. The temporal lobe is also important structure for the consolidation of memory, and when it’s injured there is potential for loss of declarative long-term memory (Lefrancois, 2012). Declarative long-term memory, or explicit memory, have a extremely important social functions because they allow us to remember and communicate what we know. Without it, we are left with only nondeclarative memory, or implicit memory. Implicit memory is useful to oneself because it’s essentially the shortcut to potentially useful reactions that we have been conditioned to. The problem with an implicit memory though, is that we can’t easily verbalize or even be clearly recalled. There is just the feeling of knowing and reacting without thought. From the research that I summarized earlier, I’ve learned that when sleep is interrupted, memory encoding is also interrupted in varying degrees. When memory cannot be encoded properly is a potential marker for more serious conditions.
What these concepts mean to me is a potential reason why I have struggled more academically then when I was a kid. I have chronic insomnia. While I’ve always know that being sleep deprived does not help with learning, I hadn’t realized how linked the two concepts are. I had always assumed that memory is formed by encoding information from the sensory parts of the brain to the hippocampus as long-term memory. What I didn’t realize was that there’re many different parts of the brain that deal with long-term memory. Likewise with concept of sleep, I thought that sleep was controlled mainly by the hypothalamus. Ends up I was wrong about that too. There is no true center of the brain that deals with sleep, and that there’s a lot of overlap between the neural networks that deal with both functions. Honestly it gives me hope that if I can overcome my insomnia that I won’t struggle as much with my academics.
The implications of these concepts in life overall is that there is more hope for other people to treat serious mental illness by rehabilitating their ability to sleep without as much disruption. This in turn, would help with being able to form and retain memory. Loss of memory is not a cause of mental illness, it seems to be a symptom.
What I liked about the topic of sleep is that there is so much to learn and there’s a lot that we don’t know about it. It doesn’t just affect memory, it also affects motivation and stress. Both concepts in turn greatly affect learning. I’m really excited to continue learning about what other problems can be potentially solved by getting a good night’s sleep.
1. Foster, R. (2013, August). Why do we sleep? [Video file]. Retrieved from https://www.ted.com/talks/russell_foster_why_do_we_sleep/details.
2. Lefrançois, G. R. (2012). Theories of human learning: What the professor said. Belmont, CA: Wadsworth.
3. Supplemental Material for Short-Term Total Sleep Deprivation Alters Delay-Conditioned Memory in the Rat. (2016). Behavioral Neuroscience. doi:10.1037/bne0000136.supp
4. Wamsley, E. J., Tucker, M. A., Shinn, A. K., Ono, K. E., Mckinley, S. K., Ely, A. V., . . . Manoach, D. S. (2012). Reduced Sleep Spindles and Spindle Coherence in Schizophrenia: Mechanisms of Impaired Memory Consolidation? Biological Psychiatry,71(2), 154-161. doi:10.1016/j.biopsych.2011.08.008
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