[A comparative electrophysiological study of regulatory components of working memory in adults and children of 7-8 years old. An analysis of coherence of EEG rhythms].

Coherence at the frequency oftheta, alpha, and beta EEG rhythms was analyzed in 14 adults and 23 children of 7-8 years old while they performed cognitive tasks requiring an involvement of working memory (WM). We used the pair matching paradigm in which subjects had to match a pair of stimuli shown in succession in the central visual field. The pairs of verbal and visuo-spatial stimuli were mixed together and presented in a pseudo random order. Each pair was preceded by a warning signal that did not specify a modality of upcoming stimuli. We analyzed EEG segments recorded (i) in the rest condition, (ii) prior to the first (etalon) stimulus (maintenance of nonspecific voluntary attention), and (iii) prior to the second (test) stimulus (retention of information in WM). In the present study we focused on the regulatory functional components of WM, and therefore, the stimulus modality has not been taken into account. In adults, maintaining nonspecific voluntary attention was accompanied by an increase of the strength of theta-related functional coupling between medial areas of the frontal cortex and temporal cortical zones and by a strengthening of local beta-related functional connectivity in the anterior areas of the central cortex. In children, no such increase was found for theta-rhythm; for beta-rhythm the increase was limited to several short-range functional links. In adults, the retention of information in WM was accompanied by the growth in alpha coherence in distant fronto-parietal links, predominantly in the right hemisphere, while in children information retention was accompanied by the growth of theta-coherence in the inferio-temporal and parietal cortical regions. The results of the study point to a relative immaturity of the mechanisms of executive control of WM in children of 7-8 years old.