The neural processing of gestures accompanying figurative speech in a narrative context in patients with schizophrenia. Preliminary results from an fMRI study

Background: Concretism – the inability to understand the abstract or figurative meaning of proverbs and metaphors represents a core feature of thought and language impairments in patients with schizophrenia (e.g. Kircher et al. 2007). Furthermore, patients with schizophrenia tend to misinterpret gestural information. So far, patient studies focused on the integration of speech and gesture on the level of words, sentences or phrases pointing to a dysfunctional involvement of the left inferior frontal gyrus (IFG) in the integration of both modalities (Straube et al. 2013). The current study aimed at extending previous findings to the investigation of gestures accompanying figurative speech in an ecologically-valid narrative context. We hypothesized, that patients with schizophrenia compared to healthy controls, demonstrate decreased activation in the left IFG for the processing of gestures accompanying figurative information in a narrative context.

Methods: During functional magnetic resonance imaging (fMRI) data acquisition, 10 patients with schizophrenia and 11 matched healthy controls were shown videos of an actor telling a short story that contained many instances of figurative language. He performed natural gestures while speaking. For analysis, sentences with figurative language in form of similes (e.g., “An X is like an Y”) had been selected from the story. These events were divided into sequences with gesture (language and gesture simultaneously: SimG condition) and without gesture (language only: SimNG condition).

Results: In comparison to the healthy control group, the patients showed abnormal activation in left inferior frontal regions, but also in neighbouring regions (e.g. the frontoparietal operculum): Patients with schizophrenia compared to control subjects showed an increased activation for the SimNG condition and a decreased activation for the SimG condition.

Conclusion: In line with our hypotheses, patients differed from healthy control subjects in the neural processing of gestures accompanying figurative speech in a narrative context. The increased neural activation in the left IFG for the SimNG condition suggests that patients need more neural resources than healthy subjects to integrate the abstract meaning of an utterance into a semantically reach environment. In contrast, patients with schizophrenia showed a decreased activation in the left IFG when gestures were used by the actor to illustrate the figurative language. These findings suggest a dysfunction in patients with schizophrenia for the processing of gestures accompanying figurative speech in a narrative context.

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