An fMRI investigation into the multifunctional role of the STS

The superior temporal sulcus (STS) has been implicated subserving speech perception, audiovisual integration, and theory of mind. Prior functional imaging studies have also reported that distinct neuronal patches within the STS region show overlapping activation in response to these three cognitive processes. This finding has led to a theory that the STS as whole, or at least parts of it, are crossmodal and multifunctional in nature, subserving multiple and different processing demands based on network connectivity. The multifunctional role of STS was investigated by applying an fMRI mixed block- and event-related design, in which 20 participants were tested on three paradigms; speech perception, audiovisual integration, and theory of mind. Data was analysed using one-way ANOVA. Individual analysis of each contrast showed activation within the STS region for all three paradigms, with speech perception and audiovisual integration activating a large bilateral posterior STS area, and theory of mind activating bilateral middle and anterior STS areas. Global conjunction analysis revealed conjunct activation in the bilateral posterior STS area, though greater in cluster size in the right hemisphere, and showed a second discrete left middle-posterior STS activated patch. The results are on the whole in line with previous research, and indicate that the posterior STS area subserves crossmodal integration and that distinct sub-structures of the STS might be multifunctional in their processing ability. This is briefly discussed in relation to the theory of network connectivity