Abnormal temporal and parietal magnetic activations during the early stages of theory of mind in schizophrenic patients

Abstract

Schizophrenia is associated with abnormal cortical activation during theory of mind (ToM), as demonstrated by several fMRI or PET studies. Electrical and temporal characteristics of these abnormalities, especially in the early stages, remain unexplored. Nineteen medicated schizophrenic patients and 21 healthy controls underwent magnetoencephalography (MEG) recording to measure brain response evoked by nonverbal stimuli requiring mentalizing. Three conditions based on comic-strips were contrasted: attribution of intentions to others (AI), physical causality with human characters (PCCH), and physical causality with objects (PCOB). Minimum norm localization was performed in order to select regions of interest (ROIs) within bilateral temporal and parietal regions that showed significant ToM-related activations in the control group. Time-courses of each ROI were compared across group and condition. Reduced cortical activation within the 200 to 600 ms time-window was observed in the selected regions in patients. Significant group by condition interactions (i.e., reduced modulation in patients) were found in right posterior superior temporal sulcus, right temporoparietal junction, and right inferior parietal lobule during attribution of intentions. As in healthy controls, the presence of characters elicited activation in patients' left posterior temporal regions and temporoparietal junction. No group difference on evoked responses' latencies in AI was found. In conclusion, ToM processes in the early stages are functionally impaired in schizophrenia. MEG provides a promising means to refine our knowledge on schizophrenic social cognitive disorders.

Keywords:

• Schizophrenia
• Social cognition
• Theory of mind
• Temporoparietal junction
• Superior temporal sulcus
• Magneto-encephalography

Acknowledgments

We would like to thank Frédéric Bergame, Antoine Ducorps, Nathalie George, Christophe Gitton and Denis Schwartz (MEG Center, Hôpital de la Pitié-Salpêtrière) for their technical support. We are thankful to Audrey Angelard, Nadine Bazin, Catherine Bourdet, Corrine Coffinier, Armelle Volkringer (Hôpital de Versailles) for their help in patients' recruitment, evaluations and/or their comments on the manuscript. This work was supported by a grant of Neuropôle (to DV), a grant of Fonds d'Etudes et de Recherche du Corps Médical (to EBP), a donation from Schizo-Oui/La Fondation pour la Recherche medicale (to AL), and an INSERM Contrat d'interface (EBG).

Notes

*The first two authors contributed equally to this work.