Changes in brain functioning from infancy to early childhood: evidence from EEG power and coherence working memory tasks.

Using measures of EEG power and coherence with a longitudinal sample, the goal of this study was to examine developmental changes in brain electrical activity during higher order cognitive processing at infancy and early childhood. Infants were recruited at 8 months of age and performed an infant working-memory task based on a looking version of the A-not-B task. At age 4.5 years, one half of the original sample returned for a follow-up visit and were assessed with age-appropriate working-memory tasks. At infancy, working memory was associated with changes in EEG power from baseline to task across the entire scalp, whereas in early childhood, working memory was associated with changes in EEG power from baseline to task at medial frontal only. Similar results were found for the EEG coherence data. At infancy, working memory was associated with changes in EEG coherence from baseline to task across all electrode pairs and by 4.5 years of age, EEG coherence changed from baseline to working-memory task at the medial frontal/posterior temporal pairs and the medial frontal/occipital pairs. These EEG power and coherence longitudinal data suggest that brain electrical activity is widespread during infant cognitive processing and that it becomes more localized during early childhood. These findings may yield insight into qualitative changes in cortical functioning from the infant to the early childhood time periods, adjustments that may be indicative of developmental changes in brain specialization for higher order processes.