As previously reported in previous sections, SCP depends on the activity of the nervous tissue. If the activity of the nerve cells is high, then the tissue is acidified and the growth of SCP occurs. At the same time, the cerebral cortex makes the greatest contribution to changes in SCP. The direct contribution of subcortical formations to the generation of SCP due to their remoteness from the recording electrodes is relatively small, but the high background activity of the cortex depends on the excitation thresholds of cortical and subcortical neurons. At low thresholds, the probability of a higher synchronized response to the afferent stimulus is high. The threshold for the excitation of neurons is to some extent related to the pH of the extracellular environment. Activation of neurons leads to acidification of the nervous tissue, which increases the threshold of excitation of nerve cells, thereby reducing their functional activity.Neural activity is regulated by a feedback mechanism (U. Bonnet et al., 2000).
When studying correlation relations, two types of patterns can be expected: first, these are correlations associated with specific sensory systems, for example, between SCP in the occipital region and the amplitude-temporal characteristics of the VEP components in the same brain region. Secondly, the relationship between the SCP and the characteristics of the VEP, reflecting the functional state of the brain as a whole and associated with non-specific brain systems. Correlations of the second kind are manifested, in particular, under stress.