FIG. 5.

Schematic representation of Granger causal connectivity between canonical speech areas during two-person dialogue with interaction (a, b) and monologue talking and listening (c, d). The directional connectivity that showed statistical inference over both surrogate and shuffled controls was illustrated in the figure. For the speaking task (b, d), the observed direction of connectivity is from Broca's area to Wernicke's area regardless of existence or inexistence of interaction. However, for the listening task, the connectivity is bidirectional including both bottom-up and top-down directions under interaction (a), whereas it is unilateral without interaction (c). The nodes were visualized with the BrainNet Viewer (Xia et al., 2013).