Sleep is one of the necessary ingredients for general well being. Those who fail to sleep properly can face a greater risk of chronic, metabolic and cardiovascular diseases. However, the brain is also affected. Sleeping paradoxically little would “fall asleep” the neurons. Brain cells would in fact become less reactive, mental faculties slowed down and cognitive performance would not be effective. This was observed by an international team of researchers from several centers including the University of California in Los Angeles (USA). Sleep deprivation alters cognitive functions, first of all short-term concentration and memory,” adds Dr. Lara Fratticci, a neurologist at Humanitas.
In the study published in Nature Medicine, researchers involved twelve patients with epilepsy to whom electrodes had been implanted in order to locate the origin of their seizures. Since lack of sleep can cause attacks, these patients remained awake all night long waiting for the onset of epileptic seizure and reduce their stay in hospital.
The research team asked these patients to recognize a set of images as quickly as possible while the electrodes recorded the “ignition”, i.e. the activation of about 1500 neurons. In particular, scientists have focused on the temporal lobe, the brain region that regulates visual perception and memory.
In the course of the research it was observed that sleep deprivation interfered with the ability of neuronal cells to communicate with each other effectively. The result: Temporary reduction of mental faculties, declining concentration, distraction, to the detriment of visual perception and memory. The neurons – observed by the researchers – worked more slowly, had a weaker activation and the process of transmission between them took much more time to achieve. Thus, sleep deprivation interfered with the ability of neurons to encode information and transform visual inputs into conscious thinking.
It’s a bit of what happens to a driver who had little sleep and a pedestrian is in front of him. His brain struggles to process the information that comes from his eyes, it takes longer than normal to realize what is in his visual field.
Researchers also saw that in the regions affected by decreased neuronal cell performance, brain waves were also slowed down: they were similar to those produced during sleep. This phenomenon – explain the authors of the study – suggests that in the selected brain regions the cells were dormant, thus leading to falls in the mental faculties, while the rest of the brain was awake and active.
In other words, it reacts differently to stimuli: “Various studies have shown that brain function remains normal for a certain period of time before it is compromised due to lack of sleep. A study suggested how latency increases when faced with visual stimuli: the stimulus was perceived as such but the subject was not able to give a meaning to what was seen. Therefore this indicates an involvement of the visual cortex,” recalls the doctor.
Little memory and out of control emotions
Among the areas of the brain where the effects of sleep deprivation are most evident is the prefrontal cortex: “This cerebral area oversees the sleep/wake cycle, and sleep-related processes. This only ensures the correct cerebral metabolism and therefore promotes the efficiency of the prefrontal cortex,” adds Dr. Fratticci.
That’s why sleep is so important: “Sleep serves to promote brain development, neuronal plasticity and learning. Several studies have shown this thanks to neuroimaging techniques: if there is sleep deprivation, anatomical alterations in the activity of this area are evident. This also impacts the process of short and long term storage, decision-making and reasoning.
The effects of blank nights also affect the hormonal system, “with increased levels of stress hormones, an additional negative factor affecting mood and efficiency of individual performance. The ability to concentrate and think is reduced, for example. Therefore, the amygdala, the part of the nervous system that regulates emotions, suffers a backlash: “You become more anxious, irritable and unable to control your emotions”, concludes Dr. Fratticci.