Sleep science expert Matthew Walker explains the effects of lack of sleep and dreams on the human body.
As several researches and statistical data have shown, the spring clock change is more taxing on the body than the autumn change, although in both cases, the change negatively affecting the body's circadian rhythm can cause problems. However, the reduction in the number of hours spent sleeping during the transition to daylight saving time makes a big difference, as the consequences of not even one hour of sleep can be seen in our psychological and physical state. Matthew Walker, sleep expert and director of the Center for Human Sleep Sciences at the University of California, Berkeley, explains the details of the process and why we need enough sleep to maintain our health in a TED video.
When a person suffers from a lack of sleep, i.e. sleeps less than the recommended eight hours, his well-being changes noticeably even after a day, and since scientists have now explored in detail the neurological processes behind the spectacular symptoms associated with it, we also know that in such cases what happens in the body and what causes the negative developments. Matthew Walker, in collaboration with Hungarian neuroscientist Jólesz A. Ferenc, professor of radiology at Harvard University, carried out the experiment, the results of which were published in the journal Current Biology in 2007 and which shed new light on the effects of sleep on brain processes: according to their observations, a excessive activity of a primitive brain region is responsible for the hypersensitivity associated with insomnia.
The amygdala is a small cluster of neurons found in the temporal lobe of both hemispheres of the human brain, which is mainly responsible for emotional responses and which is connected to other areas of the brain, such as the prefrontal cortex. The prefrontal cortex, according to Walker's description, is the brain's CEO, one of the most developed parts of our brain, which, standing at the top of the hierarchy, distributes instructions to other regions and largely determines how we make decisions and how we react in each life situation. This plays the biggest role in more complex, "higher order" forms of behavior, in the expression of our personality and in our social habits, i.e. our behavior in communities. The task of regulating the amygdala also falls to it, so our emotional responses partly depend on the functioning of the well-developed connection system between the two brain areas.
According to the results of the researchers' studies, lack of sleep impairs the proper functioning of this important connection, and because of this, the amygdala is left alone and becomes excessively active without supervision.
"Without sleep, we become a complete emotional gas pedal, with too few control brakes."
- explains Walker in his book Overnight Therapy.
The role of the prefrontal cortex, or more precisely the medial prefrontal cortex (MPFC) in emotional regulation was measured in a test involving 26 subjects, 14 of whom represented the sleep-deprived state, and 12 served as a control group. The first 14 participants could not sleep for two days and one night, during which they acquired a significant amount of sleep deprivation, while the others were allowed to have a normal night's sleep. On the second day, the subjects' brain activity was monitored with fMRI (functional magnetic resonance imaging), while they were shown images that evoked an emotional response.
According to the observations, the more negative the event shown in the recordings, the more active the amygdala became in the case of the members of both groups, however, the sleep-deprived group reacted with approximately 60% increased amygdala activity. Based on the analysis of the images, it was also determined that the connection with the MPFC was much weaker in this case, meaning that the functional connection between the two brain areas was lost.
"A night's sleep appears to reset the brain's ability to respond properly to the next day's emotional challenges,
by maintaining the functional integrity of the MPFC-amygdala system and thereby controlling the appropriate behavioral repertoire," the researchers conclude in the study.
Because of this, some level of hypersensitivity is essentially inevitable with little sleep, but it is no longer possible to clearly define what too little sleep time means and when we should sleep. According to experts, eight hours of sleep a day is necessary to maintain a healthy functioning body, not only to keep the amygdala under control, but also to regulate the production of hormones that regulate mood, hunger and sleep, and to maintain the activity of natural killer cells that protect the body against pathogens. This time, especially at once, may seem like a lot, but this is how the series of consecutive sleep phases can take place without interruption and efficiently, during which the non-REM and REM (rapid eye movement) stages follow one another.
The REM phase, which accounts for approximately 20% of sleep time, can be particularly important in terms of psychological well-being, as this is when we dream and dreams provide a kind of quick help for processing emotionally stressful events. The time spent dreaming is the only part of the day when the brain does not secrete the hormone norepinephrine, which is produced in response to stress and causes the fight-or-flight response, as well as feelings of agitation and anxiety. If, during our dreams, we relive the events of the day that caused strong emotions in us, but now without the negative hormonal accompaniment, then we have the opportunity to reprogram our responses in calmer conditions and record a more positive or at least more balanced emotional memory.
Better sleep is helped by brain training exercises, which you can learn as part of online training.