Quantitative EEG evaluation in normal elderly subjects during mental processes: age-related changes.

Computerized EEG study was performed on 39 healthy elderly subjects (50-90 years), divided into two cohorts of increasing age (old, older) and on a group of 21 young controls. The EEG was recorded at rest, with eyes closed (EC) and during blocking reaction (BR), fixation (FIX) and mental arithmetic (MA) tasks. At rest with EC, the only significant variation was an increase of beta 1 relative power in old subjects which was positively correlated with age. During the performance of the mental tasks, in the elderly population when compared to young controls, the slow activity decreased slightly or was not significantly modified, while the alpha reactivity progressively decreased, showing a negative correlation with age in the older group. Beta 2 increased significantly in elderly subjects during BR and FIX but such change was less consistent with increasing age. Data show that at rest, the EEG in the elderly population differs only from that of young controls by showing a more pronounced fast activity, while only during mental processes is it possible to evidence changes that can be utilized as physiological "markers" of normal aging.