In the transition from wakefulness to sleep, in parallel with the increase in slow-wave activity on the EEG, cerebral energy metabolism decreases. Local cerebral blood flow and oxygen consumption by the brain decrease during sleep by 10.2 and 7.6% of the x level during wakefulness. A significant decrease in local cerebral blood flow, according to PET with H 2 15 O, was detected during slow-wave sleep in the brain stem, thalamus, basal ganglia, as well as in heteromodal associative areas (prefrontal and lower dark), while in the primary projection areas of blood flow reduction not observed . During the 3rd and 4th stages of slow-wave sleep, according to PET, the level of glucose consumption decreases in the hemispheres by 31%, in the thalamus and in the cerebellum by 33%, in the brain stem by 25% . According to glucose consumption data, sleep with fast eye movements is characterized by activation of the bridge, thalamus, lateral hypothalamic regions, amygdala, anterior cingular cortex and islet with a decrease in activity in the prefrontal region .
The dynamics of soft starters reflects changes in the FS. When the SCP is withdrawn directly from the brain in animals during falling asleep, a positive shift in the SCP is observed, apparently due to hyperpolarization of the neurons of the cortex . In humans, in the transition from wakefulness to slow-wave sleep, on the contrary, a negative shift in SCP was revealed, which indicates a different genesis of potential changes than that recorded from the brain in animals. In the case of the location of the active electrode on the vertex, and the reference one on the earlobe, the shift of the SCP to the negative side was 0.5-0.75 mV . Apparently, the negative shift in SCP during registration from the surface of the head is explained not by depolarization of cortical neurons (during slow-wave sleep, inhibitory processes prevail in the cortex), but by a decrease in energy metabolism and, accordingly, a change in the CSR of the blood flowing from the brain to the alkaline side. It was revealed that at night, in subjects deprived of sleep, SCP was significantly less than in the control group with drinkers . According to N.A. Aladzhalova , sleep and some types of anesthesia, in particular nembutal, are also accompanied by negative changes in SCP. The difference in the values of constant potentials recorded during sleep and during the wakeful period in humans can reach several millivolts. Such a large difference in the amplitude of the shifts in different studies is associated with registration features, namely, the location of the reference electrode. So, when the electrode is placed on the ear or other parts of the head, the shift of the SCP is less than if the reference electrode is located on the limbs. The reason for this lies in the features of cerebral and extracerebral blood supply to the head and is discussed in detail in chapters 3 and 4, and in section. “The effect of hyperventilation on brain energy metabolism” in this chapter.
So, during the transition from wakefulness to sleep, cerebral blood flow and energy metabolism decrease in the associative areas of the human cerebral cortex, which is reflected in the negative shift of SCP on the surface of the head. When registering from the surface of the brain, the process of falling asleep is accompanied by a positive shift in SCP, reflecting the hyperpolarization of neurons and glia in the cortex.