A comparative electrophysiological study of regulatory components of working memory in adults and seven- to eight-year-old children: An analysis of coherence of EEG rhythms

Abstract

Coherence at the frequency of θ, α, and β 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 visuospatial 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 (reference) stim� ulus (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 vol� untary attention was accompanied by an increase of the strength of θ�related functional coupling between medial areas of the frontal cortex and temporal cortical zones and by a strengthening of local β�related func� tional connectivity in the frontocentral areas of the cortex. In children, no such increase was found for θ rhythm; for β rhythm the increase was limited to several shortrange functional links. In adults, the reten� tion of information in WM was accompanied by the growth in α coherence in distant frontoparietal links, predominantly in the right hemisphere, while in children information retention was accompanied by the growth of θ coherence in the inferiotemporal and parietal co rtical 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.