Reduced language lateralization in first episode schizophrenia: A near infrared spectroscopy study

Background: Diminished functional lateralization in language-related areas is found in chronic schizophrenia (SZ). However, whether this reduced lateralization exists at the early stage of SZ remains unclear. The present study aimed to investigate language lateralization in first episode schizophrenia (FES) using near infrared spectroscopy (NIBS) during a letter version of verbal fluency test (VFT). Methods: A total of 28 FES patients and 33 healthy controls (HCs) underwent NIBS while performing a VFT. Six regions of interests (ROIs) were defined: the bilateral frontal-, inferior frontal gyrus (IFG), and temporal regions. Laterality index (LI) was calculated and compared between the two groups in ROIs. In addition, we investigated whether language lateralization was correlated with severity of clinical symptoms. Results: Across all ROIs, LI was significantly reduced in FES patients (p = 0.037) compared to controls in the IFG region. In addition, LI was not found to be correlated with VFT performance, the PANSS positive, negative or general psychopathology subscales. Conclusions: Our study demonstrated a diminution of leftward functional lateralization in the IFG during a VFT in FES patients. This is the first NIBS study to report reduced functional lateralization in patients at the early stage of schizophrenia.