ALPHA-RESPONSE SYSTEM IN CHILDREN - CHANGES WITH AGE

Evoked and event-related brain potentials (EPs, ERPs) may be regarded as originating from the reorganization of the spontaneous EEG rhythms (Baqar, 1980). Until now, no data is available about the development o f the evoked frequency components in EPs and ERPs of children. The mai n objective of the present research was to study the alpha response sy stem in 6-11-year-old children. We suggested that the ability to reorg anize the alpha activity and produce repeatable alpha patterns after e xternal stimulation might undergo developmental changes that could ref lect certain changes in information processing with increasing age fro m childhood to adulthood. Fifty 6-11-year-old children divided into fi ve age groups, and 10 young adults were studied in a passive and an od d-ball condition. Alpha responses in the auditory EPs and non-target E RPs at Fz, Ct and Pt were analyzed. The magnitude and phase-locking wi th stimulus of single alpha responses were evaluated in the first 300 ms of the post-stimulus epoch. An original method was applied to asses s quantitatively the repeatability (phase-locking) of the evoked alpha oscillations. The magnitude and the phase-locking to stimulus were an alyzed with respect to their dependence on the age and topography fact ors. Our main results show that the alpha responses in 6-11-year-old c hildren are different from those in adults: (1) Adults had significant ly lower amplitude and stronger phase-locking than children; (2) Adult s had maximal alpha amplitudes and phase-locking over the vertex, wher eas children displayed maximal responses over the parietal site; (3) T he phase-locking of eldest (10-11-year-old) children was as strong as in adults. Whereas no difference existed between groups of children in alpha response amplitudes, a significant increase in phase-locking fr om 6 to 11 years was observed. Concerning the obtained results we sugg est that (1) Alpha response system is functionally involved in 6-11-ye ar-old children, though its development is not complete at the age of 11, the upper limit of our sample; (2) With regard to their differenti al developmental time-courses, the magnitude and the phase-locking par ameters might be suggested to relate to different functional aspects o f the alpha response system. The applied original method makes it poss ible to analyze the phase-locking to stimulus (or phase-reordering) se parately and independently from the amplitude (enhancement) of the fre quency responses, thus providing for a deeper examination of the evoke d frequency components. (C) 1997 Elsevier Science B.V.