Have a good sleep before an exam: why is it important?

Exam sessions, exercises, deliveries, deadlines... the daily commitments of a student often prevent a peaceful rest. Why is it important to sleep adequately in the days before an important exam?

Sleep stages

Before discussing the fundamental role of sleep, it is necessary to briefly review the stages of sleep.

1. Falling asleep; this transition phase between wakefulness and sleep generally lasts a few minutes; the body begins to relax the muscles and slow heart rate, breathing and eye movements.
   
2. Light sleep; light sleep phase preceding deep sleep. Heart rate and breathing slow down and muscles relax. Body temperature drops and eye movements stop. Brain wave activity slows down but is characterized by short episodes of electrical activity.
3. Deep non-REM sleep; it occurs in longer periods during the first half of the night. At this stage, heart rate and breathing are reduced to a minimum, and episodes of sleepwalking or sleep talking may occur. Brain waves become even slower, which is why it is also referred to as slow wave sleep.
4. REM sleep; the acronym REM stands for rapid eye movements since, in this phase, eye muscles are the only one that are active, moving rapidly from side to side behind the eyelids. Brain wave activity approaches that observed during wakefulness, breathing becomes faster and more irregular and blood pressure and heart rate increase until they reach wakefulness levels. During REM sleep, most of our dreams happen: if we wake up at this stage, we will remember particularly well what we dreamt of.

Sleep consolidates the memory

Sleep plays a fundamental role in the consolidation of memory (during sleep, we insert into "memory storage" what we have learned during the day). Delta waves (slow and large-amplitude waves that characterize deep non-REM sleep) mainly favor the storage of information learnt during the day: during this phase of sleep, the lowest levels of acetylcholine are recorded [a neurotransmitter responsible for nerve transmission in the central and peripheral nervous system, Ed.]. In the daytime, on the other hand, acetylcholine is present in high levels since it is necessary to capture new information.

However, recent studies have shown that while non-REM deep sleep is critical for information storage, REM sleep plays an important role in accurately retrieving the information. It is interesting to remember that the first evidence that the night rest was protective towards the natural forgetting of situations and things dates back to 1924, when the different phases of sleep were not yet known.

Sleeping also allows the anterior areas of the brain to "rest", which are important during the day for attention, judgment and the ability to make associations, integrating the functioning of memory.

Even a short nap can help

Even a short afternoon nap can help you memorize better. In this regard, a recent research compared subjects who habitually took an afternoon nap with subjects without this particular habit: the authors of the study found that the nap led to a significant improvement in memory tests in both groups of subjects.

Sleep is sensitive to activating substances

Sleep is very sensitive to coffee, nicotine and activating substances: attention must me paid, since they tend not only to increase the latency of falling asleep, but also to reduce deep non-REM sleep (the most important for the storage of information) .

Sometimes alcohol is used to promote falling asleep and reduce anxiety levels. We must be careful, because if alcohol allows us to fall asleep earlier, it has a negative effect on the continuity of sleep.

Sleeping relieves stress

Finally, sleep is an important inhibitor of the stress hormone cortisol; cortisol, in the event of sleep deprivation, remains high and negatively interacts with the amygdala, part of the brain that regulates emotions. Strong emotions are known to erase recent memories before taking an exam.