Changes during aging in the electroencephalographic cortical synchronization under visual stimulation

This paper analyzes changes during aging in the electroencephalographic (EEG) synchronization between different areas of the cerebral cortex in healthy elderly subjects under visual stimulation. Two groups were selected: one (A) of 10 adults aged 50-65 years and another (B) of 15 subjects aged 66-80 years. EEG recordings of 16 "monopolar" channels were carried out (digitized at 256 Hz), all referenced to the mean and following the standard 10-20 system, and were performed at rest with eyes closed under visual stimulation. From an index (L) of nonlinear generalized synchronization, the average cortical synchronization (ACS) of each channel with the rest and the corresponding average asymmetry in the synchronization (ACM) was estimated. Changes with age (A vs. B) in cortical synchronization and in average interhemispheric asymmetry for all cortical areas were estimated via a repeated measures MANOVA. The results show that under visual stimulation, the SCM decreases with age for most channels (p < 0.01) except for the frontals. The channels that showed asymmetry in the synchronization (p < 0.01) were the frontals F3, F4 y Fp2, the parietal P3 and the temporal T5, in all of them a significant reduction in asymmetry with age (p < 0.01) was observed.