Increased SCD in epilepsy reflects the development of acidosis in the brain, resulting from the characteristic changes in energy processes. During convulsive states, glycolysis increases, and the content of lactic and pyruvic acids increases in different parts of the brain. Therefore, during discharges of a population of epileptic neurons, a strong metabolic acidosis is observed in the brain (pH up to 7.24). The activity of mitochondrial enzymes (succinate dehydrogenase, cytochro-oxidase and glutamate dehydrogenase), on the contrary, decreases. The energy of the respiratory chain “leaks” to non-phosphorylating processes associated with epileptogenesis (KI Pogodaev, 1986).
Between the parameters of the SCP and EEG revealed a significant correlation. That
the correlation reaches only an average level; it can be connected both by a complex relationship between the functional activity and the energy metabolism of the brain, and a certain influence of extracerebral processes on the brain SCP.
In general, the data obtained allow us to characterize the relationship between SCP and EEG as follows. With low functional activity of the brain and low cerebral energy metabolism, low SCP is recorded, the relative spectral power of the alpha rhythm is lowered, and theta and delta activities are increased. With an increase in the functional activity of the brain to the optimum level, the relative spectral power of the alpha rhythm increases, while the slow-wave activity decreases, which is accompanied by an increase in energy exchange, a slight acidification of the brain and, accordingly, an increase in UPP. The increase in the functional activity of the brain, accompanied by depression of the alpha rhythm (desynchronous type of EEG), is associated with increased energy metabolism and increased UPP. The appearance of bilateral-synchronous epileptiform activity on EEG,in which the relative power of the alpha rhythm decreases and the relative power of slow-wave activity increases, it is accompanied by a significant increase in UPP, apparently related to the transition to anaerobic oxidation and the accumulation of lactate in the nervous tissue.
The relationship of cerebral energy metabolism and evoked potentials
Interest in the study of the relationship between cerebral energy processes and the function of nerve cells associated with the transmission and processing of sensory information, due to the fundamental importance of this issue and its little knowledge. According to PET, the more nerve centers are involved in activities related to the processing of information, the higher the consumption of glucose and the more markedly acidification of the nervous tissue occurs. However, this question is not so simple, since it is clear that the relationship between extracellular pH and neural activity is non-linear, and the relationship between the dynamics of induced potentials (TL) and SCP depends on the original functional state of the brain.
This section is devoted to the interaction of energy and information processes. For this purpose, the correlation dependences between the characteristics of EPs of different genesis and SCP indicators are analyzed.
Under EP, electrophysiology implies a certain sequence of positive and negative fluctuations of the potential difference of the microvolt range, arising in different parts of the brain in response to the action of some afferent stimulus. Depending on the type of stimulation, there are visual, auditory, somatosensory, and other EPs. Due to the fact that the EEG waves can mask EP, currently they use the technique of averaging the electrical reactions of the brain in response to a repeatedly repeated afferent stimulus. The positive and negative fluctuations of the evoked response are numbered, and they are called VP components; they are described using time and amplitude parameters. Temporal characteristics or latent periods are the time from the moment of presentation of the afferent stimulus to the positive or negative peak of the corresponding EP component.The amplitude of the components is measured from “peak to peak” or from the midline to the maximum of the corresponding EP component. In the visual evoked potentials (VEP), as a rule, there are three positive (P1; P2; P3) and three negative (N1, N2, N3) components. The early components of P1 and, to some extent, N1 reflect the response of the cortex to impulses coming along specific visual pathways with a relatively small number of synaptic switches. Late components (P2, N2; P3, N3) occur in the cortex in response to impulses coming in via polysynaptic reticulo-limbic-cortical systems of the brain.The early components of P1 and, to some extent, N1 reflect the response of the cortex to impulses coming along specific visual pathways with a relatively small number of synaptic switches. Late components (P2, N2; P3, N3) occur in the cortex in response to impulses coming in via polysynaptic reticulo-limbic-cortical systems of the brain.The early components of P1 and, to some extent, N1 reflect the response of the cortex to impulses coming along specific visual pathways with a relatively small number of synaptic switches. Late components (P2, N2; P3, N3) occur in the cortex in response to impulses coming in via polysynaptic reticulo-limbic-cortical systems of the brain.