Background: Cross-sectional functional imaging studies have shown a reduced leftward language lateralization in schizophrenic patients. An unanswered question is whether this reduced leftward lateralization is stable over time or is modified over the course of the illness.
Methods: Ten right-handed (RH) patients (DSM-IV) and 10 RH controls were matched one-to-one for sex, age, and level of education. The subjects underwent two separate fMRI sessions while engaged in a story listening task, 21 months apart. After each session, story comprehension (task performance) was assessed through a 12-item questionnaire. The stability of the decreased asymmetry indices in the semantic region of interest (LANG) was investigated with an ANOVA to compare groups and sessions. In order to test the evolution of functional asymmetry indices at an individual level, a linear correlation between both fMRI session asymmetry indices was calculated in all subjects. Correlations between asymmetry indices and the severity of psychotic symptoms or task performances were computed.
Results: The asymmetry indices of the LANG were significantly reduced in patients as compared to controls and strongly correlated between sessions. Values of asymmetry indices were unrelated to either psychotic symptoms or task performances.
Conclusions: This reduced leftward lateralization for language did not vary over time and was not influenced by the psychosis severity or the task performances. This result reinforces the hypothesis that schizophrenia is characterized by a particular organization of language.