Impaired temporoparietal deactivation with working memory load in antipsychotic-naïve patients with first-episode schizophrenia.

OBJECTIVES: Neuroimaging studies have shown abnormal task-related deactivations during working memory (WM) in schizophrenia patients with recent emphasis on brain regions within the default mode network. Using fMRI, we tested whether antipsychotic-naïve schizophrenia patients were impaired at deactivating brain regions that do not subserve WM.
METHODS: Twenty-three antipsychotic-naïve patients with first-episode schizophrenia and 35 healthy individuals underwent whole-brain 3T fMRI scans while performing a verbal N-back task including 0-back (no WM load), 1-back (low WM load), and 2-back (high WM load) conditions.
RESULTS: Contrasting the 2-back and 0-back conditions revealed that patients deactivated default mode network regions to a similar degree as controls. However, patients were impaired in deactivating large bilateral clusters centred on the superior temporal gyrus with increasing WM load. These regions activated with the no WM load condition (0-back) in both groups.
CONCLUSIONS: Because 0-back activation reflects verbal attention processes, patients' persistent activation in the 1-back and 2-back conditions may reflect an inability to shift cognitive strategy with onset of WM demands. Since patients were antipsychotic-naïve and task performance was equal to controls, we infer that this impaired temporoparietal deactivation may represent a primary dysfunction in schizophrenia.