Figure 6

Dynamic causal modelling (DCM) of connectivity using event-related responses across the six main regions involved in audio-visual speech integration. The circles represent the sampled sources: primary auditory cortex (PAC), mediotemporal cortex (MT), the superior temporal gyrus (STG), the left superior temporal sulcus (STS), the inferior frontal gyrus (IFG) and the anterior temporal cortex (ATC). All connections and their values reflect enhanced or reduced connectivity of fusion (A) and combination (B) responses, relative to responses in the congruent condition. (A) Fusion was associated with increased connectivity from the STS to ATC and MT. Xonnectivity also increased from MT to PAC and decreased from PAC to ATC during fusion. (B) Combination was associated with increased connectivity from IFG and PAC to STS. Connectivity also increased from PAC to both STS and IFG, and decreased from STS to ATC, from ATC to IFG, from STG to PAC. We tested the differences between conditions using Parametric Empirical Bayes (PEB) models. Rather than comparing different network architectures, we performed a post-hoc search by pruning away parameters that did not contribute to the model evidence (P < 0.05). These results in a sparse graph where the connections shown are those that contributed significantly to the model evidence. Red dotted lines: reduced connectivity; Blue lines: enhanced connectivity. Image made using Microsoft PowerPoint, version 16.41.