Temporal Dynamics and Cortical Networks Engaged in Biological Concepts Encoding

The present EEG study examined the temporal dynamics and cortical networks of theta, alpha and beta bands that were engaged in the encoding of concrete biological concepts presented as words and pictures. The frontal midline exerted similar levels of theta augmentation in both the picture and word conditions. The occipital and central parietal’s event-related spectral perturbation (ERSP) and reaction-time sorted spectral (RTSS) images showed strong theta augmentation precisely time-locked to stimulus onsets, tightly followed by strong alpha/beta
suppression in both conditions. The cortical network was measured by component event-related coherence (ERCoh) between time courses of component pairs. The continuous and pronounced theta, alpha, and beta
coherence between the occipital and central parietal regions was found for both conditions. In contrast, the theta, alpha and beta coherences between the frontal midline and occipital, and the frontal midline and central parietal regions were observed as discrete patterns. Examining temporal dynamics and coherence patterns in the occipital and central parietal regions, it suggested the possibility that these two regions work collaboratively to select relevant sensory stimuli and process each sensory stimulus through the consecutive coherence of theta, alpha, and beta. The frontal midline area might maintain working memory processing through scattered coherence rather than continuous coherence in order to coordinate with either the occipital or central parietal areas.