Since the change in cerebral functions in ontogenesis is uneven, we distinguish a number of age intervals, which are decisive for describing the dynamics of the FMA. Below are the values of interhemispheric potential difference in different age groups .
The average values of the inter-hemispheric difference SCP in the temporal leads in right-handed men and women of different age.
The ordinate is the value of SCP. The abscissa is age. The black bars are the arithmetic average values of the inter-hemispheric difference UCP in the temporal leads in men; gray bars – the same for women; uncolored rectangles – standard error.
* – reliably differing from zero ( p <0.05) values of the hemispheric difference SCP.
It can be seen from the figure that the hemispheric difference between SCP has different age dynamics in men and women. In girls, earlier, by the age of 9, a stable potential difference is formed with a predominance of SCP in the left hemisphere, which is consistent with the data on their earlier maturation of the brain. Formation of peculiar hemispheric differences for adults SCP is one of the factors determining the success of training (section 10.2 “Functional energetic states of the brain and the learning process among younger students”). In men, significant hemispheric differences of SCP are formed somewhat later, but they persist longer – up to 60 years.
Significant differences between men and women occur only at an early age. This allows in many cases to combine in a single group of subjects of different sexes. In young and mature ages, the SCP values in the left dominant hemisphere are statistically significantly higher than in the right. The steady difference in SCP between symmetric temporal regions indicates that the temporal region of the left dominant hemisphere and in men and women over a fairly significant life span requires more energy than the corresponding region of the right hemisphere.
Reduction of motor asymmetry in healthy subjects of senile age was also revealed during behavioral testing. The decrease in hemispheric differences seems to reflect involutional processes that reduce the specialization of the hemispheres. The smoothing of interhemispheric asymmetry is obviously associated with changes in the cerebral blood flow, which decreases more significantly in the left hemisphere during aging. The variance of the hemispheric difference SCP in the temporal leads increases about two times in the elderly and senile age compared with the same indicator in children, young and mature. This is obviously associated with an increase in interindividual variability of interhemispheric asymmetry in old age due to the fact that involutional processes may prevail in different subjects either in the left or in the right hemisphere.