Otherwise, this careless behavior would have been phased out by evolution centuries ago. Brain Plasticity Theory is probably one of the more recent, and rather compelling, theories of sleep. It is based on research findings, which suggest that sleep is correlated to changes in the organisation and structure of the brain.
In earlier days, the brain was perceived as a static organ, but many studies have since disproved this notion by showing that, the brain has the ability to adapt and change over time. To start with, the brain plasticity theory argues that, people sleep so as to process the information they have acquired during the day and consolidate new memories. It suggests that, when one is asleep, the brain does not rest idly, but rather, it utilises this time to sort out and review the activities and information absorbed throughout the day, and cements these things into long-term memory.
Support for this hypothesis has been drawn from several studies, which demonstrate that lack of sleep has a negative impact on the ability to remember information. For instance, in one experiment a number of volunteers were given aptitude tests such as remembering a sequence of patterns presented to them on a computer.
Half of the volunteers were shown these patterns during the morning session, and the other half in the evening, after which, their memories were tested by the team of researchers. For the morning volunteers, the test was done after a full day of being awake while the evening learners were tested after a night's sleep; and sure enough, the individuals allowed to sleep had better recollection of the test patterns.
The argument presented above can also be used to explain why sleep is vital in the brain development of infants and young children. That is, the same reasoning can be used to argue that, the reason why infants spend a huge part of their lives sleeping about 13 to 14 hours of sleep every day is because at this stage, babies are constantly learning about the world around them and hence, they require more deep sleep for them to process all this information.
In natural selection, competition for and effective utilisation of energy is extremely important — in that, if a species is able to make use of its given energy resources in a slightly more effective manner, it would have a great advantage over similar species. Generally, our body temperature and caloric demand tends to drop during periods of sleep, and increases when we are awake. It is such evidence which gives support to this intriguing hypothesis that, indeed, sleep does play a role in helping organisms to conserve their energy resources.
Some researchers actually consider this idea to be part of and, correlated to, the evolutionary theory of sleep. Further Reading If you enjoyed this article you will find the below of interest: How to sleep cool this summer The ultimate sleep improvement checklist How sleeping with your phone is harming your life.
This is a segment of a polysonograph PSG , a recording of several physical variables during sleep. The x-axis shows passage of time in seconds; this record includes 30 seconds of data. The location of the sets of electrode that produced each signal is labeled on the y-axis. The red box encompasses EEG output, and the waveforms are characteristic of a specific stage of sleep.
Other curves show other sleep-related data, such as body temperature, muscle activity, and heartbeat. Sleep-wake cycles seem to be controlled by multiple brain areas acting in conjunction with one another. Some of these areas include the thalamus, the hypothalamus, and the pons.
As already mentioned, the hypothalamus contains the SCN—the biological clock of the body—in addition to other nuclei that, in conjunction with the thalamus, regulate slow-wave sleep. Sleep is also associated with the secretion and regulation of a number of hormones from several endocrine glands including: melatonin, follicle stimulating hormone FSH , luteinizing hormone LH , and growth hormone National Institutes of Health, n.
You have read that the pineal gland releases melatonin during sleep [link]. Melatonin is thought to be involved in the regulation of various biological rhythms and the immune system Hardeland et al. During sleep, the pituitary gland secretes both FSH and LH which are important in regulating the reproductive system Christensen et al. The pineal and pituitary glands secrete a number of hormones during sleep. Given the central role that sleep plays in our lives and the number of adverse consequences that have been associated with sleep deprivation, one would think that we would have a clear understanding of why it is that we sleep.
Unfortunately, this is not the case; however, several hypotheses have been proposed to explain the function of sleep. One popular hypothesis of sleep incorporates the perspective of evolutionary psychology.
Evolutionary psychology is a discipline that studies how universal patterns of behavior and cognitive processes have evolved over time as a result of natural selection. Variations and adaptations in cognition and behavior make individuals more or less successful in reproducing and passing their genes to their offspring. One hypothesis from this perspective might argue that sleep is essential to restore resources that are expended during the day.
Just as bears hibernate in the winter when resources are scarce, perhaps people sleep at night to reduce their energy expenditures. While this is an intuitive explanation of sleep, there is little research that supports this explanation. In fact, it has been suggested that there is no reason to think that energetic demands could not be addressed with periods of rest and inactivity Frank, ; Rial et al. Another evolutionary hypothesis of sleep holds that our sleep patterns evolved as an adaptive response to predatory risks, which increase in darkness.
Horne proposed a theory which combined both the restorative and evolutionary theories to explain the functions of sleep. He said there are two types of sleep, core which is needed and optional sleep. Horne proposed that the restorative approach can explain why we need core sleep, whilst the optional sleep can explain why we might sleep to waste time and conserve energy.
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