American scientists have found that the link between sleep deprivation and greater susceptibility to pain is responsible not only for the somatosensory cortex, but also for other areas, such as the proportion of the islet and the nucleus accumbens, which “decide” whether the stimulus causes pain or not. magnetic resonance experiment with people who spent the night in the laboratory. The article was published in Journal of Neurology.
Scientists have repeatedly demonstrated the relationship between lack of sleep and increased nociception: in laboratory conditions, both in humans and in animals, susceptibility to the effects of pain stimuli increases with lack of sleep. However, the regulation of the brain is almost unknown: in addition to the somatosensory parts of the brain, which are responsible for processing the signals received by the receptors in the skin, other parts of the brain can also be sensitive to lack of sleep. In addition, it is not known how changes in sleep affect the pain threshold of the individual.
It decided to find scientists led by Adam Krause of the California Institute of Berkeley, who conducted two studies with people in the laboratory and an online survey. The first experiment involved 25 volunteers, each of whom spent two nights in the laboratory: one with eight hours of sleep and the other without sleep (the interval between two nights was at least one week).
The pain threshold of each of the participants was measured with heat: to do this, a special heating device was placed on the skin of the left leg, the temperature of which gradually increased by one degree. The participants in the experiment were asked to note the moment when the pain from the effects of the temperature stimulus reached seven points on a ten-point scale.
Morning after night, the pain threshold of the participants was again checked in the laboratory. Scientists have discovered that insomnia at night significantly reduces the pain threshold of participants: lack of sleep leads to a decrease in temperature, which is considered unpleasant.
Brain was also observed
In addition, scientists conducted an experiment with functional magnetic resonance imaging to study brain activity when exposed to painful and neutral stimuli. As expected, the effects of painful high temperatures increased the activity of the somatosensory cortex. A decrease in activity was observed in the thalamus and the nucleus accumbens – the part of the brain that is involved in the formation of the pain threshold (that is, decides whether pain is stimulated) or in the lobe of the islet. whose damage leads to abnormal perception of pain.
The online survey on the effects of sleep deprivation on pain was attended by 236 volunteers who reported experiencing pain of a different nature (for example, chronic pain or pain after fractures). Each participant passed two surveys: in the morning, to report how well they slept, and at night, to report how strong their sense of pain was during the day.
The authors concluded that lack of sleep reduces the pain threshold of people, which makes them more susceptible to nociceptive stimuli. The mechanism of this is not limited to hypersensitivity, as can be seen in the activity of the somatosensory cortex, but also applies to the type of suppression of those parts of the brain that determine whether the stimulus is physically unpleasant or not.
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