Local SCP associated primarily with temporal parameters REG: most often a negative correlation is found with – time slow blood supply, and – total time of fast and slow blood supply. It is clear that the higher the intensity of energy metabolism, the higher the rate of blood filling in general and the lower the values of indicators 1 and 2.
It should be noted that the main correlation links of the characteristics of the SCP occur with the REG parameters in the mastooccipital lead: 69 correlation coefficients that are significantly different from zero at p <0.05. In this case, the correlation analysis found only 6 reliable correlation coefficients between the SCP and the REG in the frontomastoidal lead. The REG in the mastooccipital lead contains information about the blood supply in the basin of the vertebral arteries that feed the occipital parts and the trunk, which regulates energy metabolism in various areas of the brain. It is natural that the amplitude parameters of the REG positively correlate with the SCP in monopolar leads and the average SCP.
The mediated effect of brain activity on the blood supply is most noticeable when studying the correlation of the hemispheric difference SCP with the indicators of REG. Interestingly, in the table. such correlation coefficients most. These tables present data on the negative correlation between the temporary indicators of REG, characterizing the rate of blood circulation, and inter-hemispheric potential difference. As shown in Chapter 11, the hemispheric difference between SCP is closely related to the level of stress at which the blood supply to the brain changes significantly, the blood filling time decreases vessels due to increased vascular tone and increased cardiac output. Amplitude parameters due to an increase in vascular tone may also decrease. Apparently, it is precisely this that explains the relationship between the inter-hemispheric difference of SCP and the REG indicators.
In addition, it was found that the correlation of the UPP with the amplitude characteristics of the REG in the left-side mastooccipital lead prevails (Table 8.11 B). This fact is currently quite difficult to explain. It is possible that the asymmetry of the cerebral blood supply with a predominance of blood flow in the left dominant hemisphere (in right-handers) plays a certain role.
Thus, the correlation of the characteristics of the REG and SCP confirms data on the relationship of the blood supply system of the brain and energy metabolism.
Such a correlation is a consequence of both direct and indirect interaction between the two systems.
Conclusion
The study of the relationship between the activity of the brain and its energy metabolism has now received new perspectives thanks to the ability to record indicators of cerebral energy metabolism and functional activity directly in the process of human life. This allows us to study the regulation of neurophysiological and energy processes in various functional states in normal and pathological conditions.
The maximum relative spectral power of the EEG alpha rhythm, corresponding to the state of calm wakefulness, is observed in a certain range of SCP, the boundaries of which are close to the average values of SCP characteristics in a population of healthy people. A lower alpha rhythm value is recorded both with a decrease and with an increase in the level of energy metabolism. Normally, a decrease in cerebral energy exchange, and consequently, SCP, is associated with a decrease in the functional activity of the brain and low alpha activity. The increase in energy metabolism is due to the increase in brain activation, in which a decrease in the relative spectral power of the alpha rhythm is also observed. This dependence explains why the success of various types of activity is maximum at a certain level of stressful arousal, and at a lower or higher level, it falls.A similar pattern exists between stressful arousal and health (D. Everly, R. Rosenfeld, 1985).
A significant increase in UPP reflects the pH shifts in the acidic direction, which may be associated with increased anaerobic energy metabolism and the accumulation of lactic acid. Lactate causes more pronounced pH shifts than carbon dioxide resulting from aerobic oxidation. Therefore, a significant rise in SCP, as a rule, is associated with the transition to anaerobic metabolism, which causes disruption of the brain, reflected in the pathological EEG activity.
The correspondence between brain activity and its energy supply is realized mainly at the cellular level. When neurons are excited, the ATP / ADP ratio changes, which affects the activity of the enzymes of the main pathways of brain energy metabolism – glycolysis and the Krebs cycle. Cerebral structures that regulate the functional activity of large populations of neurons have a significant impact on the level of cerebral energy metabolism.
These structures should primarily include the stem reticular formation, which regulates the activity of large areas of the cortex and thereby affects their energy metabolism. Therefore, an increase in the energy exchange in the cortex is closely related to the activation of stem structures. This is manifested in the correlation of the parameters of the auditory evoked potentials of the brain stem and SCP.
The systemic factor associated with the regulation of energy metabolism is stress, which activates the structures of the limbic-reticular complex and the hypothalamic-pituitary-adrenal axis. Under the influence of stress, functional hemispheric asymmetry changes (LR Zenkov, P.V. Melnychuk, 1985; V.P. Leutin, E.I. Nikolayeva, 1988; V.F. Fokin, N.V. Ponomareva, 2001) . A significant increase in functional activity, which is observed under stress, is usually accompanied by an increase in hemispheric asymmetry. The reasons for this are discussed in Chapter 11.
To maintain a higher energy metabolism in conditions of increased functional activity, it is necessary to strengthen the local cerebral blood flow, which is achieved mainly due to its metabolic regulation. LMC increases with the increase in the extracellular medium of potassium ions and hydrogen, which accumulate when neurons are activated.
On the other hand, changes in energy metabolism affect the functional activity of the brain. The most striking example is hypoxia, which, depending on the degree of severity, causes various disruptions of nerve cells. Hypoxia in conditions of hyperventilation can provoke the appearance of pathological activity in the EEG due to changes in postsynaptic potentials during energy deficit. Significant factors affecting cerebral energy metabolism are changes in blood circulation or metabolic abnormalities, leading to insufficient oxygen and glucose intake in the body. The relationship between blood circulation parameters and energy exchange is clearly seen in the correlation between blood flow and SCP. Normally, an increase in the amplitude characteristics of a REG is associated with an increase in SCP.
Another factor that ensures an adequate match between energy metabolism and functional activity is negative feedback on the final products of energy metabolism. With the enhancement of the functional activity of the brain and the increase in energy processes, the formation of acidic energy exchange products is enhanced, while acidosis in most cases reduces the excitability of neurons. The inhibitory effect of acidification on the functional activity of the brain can be seen in the example of the negative correlation between the UPP of the brain and the amplitude of visual evoked potentials.
Due to these mechanisms of regulation, the functional activity of the brain and its energy metabolism are closely interconnected, which suggests a single energy-information state of the brain.