Superior temporal sulcus disconnectivity during processing of metaphoric gestures in schizophrenia.

The left superior temporal sulcus (STS) plays an important role in integrating audiovisual information and is functionally connected to disparate regions of the brain. For the integration of gesture information in an abstract sentence context (metaphoric gestures), intact connectivity between the left STS and the inferior frontal gyrus (IFG) should be important. Patients with schizophrenia have problems with the processing of metaphors (concretism) and show aberrant structural connectivity of long fiber bundles. Thus, we tested the hypothesis that patients with schizophrenia differ in the functional connectivity of the left STS to the IFG for the processing of metaphoric gestures. During functional magnetic resonance imaging data acquisition, 16 patients with schizophrenia (P) and a healthy control group (C) were shown videos of an actor performing gestures in a concrete (iconic, IC) and abstract (metaphoric, MP) sentence context. A psychophysiological interaction analysis based on the seed region from a previous analysis in the left STS was performed. In both groups we found common positive connectivity for IC and MP of the STS seed region to the left middle temporal gyrus (MTG) and left ventral IFG. The interaction of group (C>P) and gesture condition (MP>IC) revealed effects in the connectivity to the bilateral IFG and the left MTG with patients exhibiting lower connectivity for the MP condition. In schizophrenia the left STS is misconnected to the IFG, particularly during the processing of MP gestures. Dysfunctional integration of gestures in an abstract sentence context might be the basis of certain interpersonal communication problems in the patients.