Reduced language lateralization in first-episode medication-naive schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Reduced functional lateralization in language areas is observed in chronic schizophrenia.
• The timing of these lateralization abnormalities and medication effects remain unclear.
• Previous studies on the link between reduced language lateralization and positive schizophrenia symptoms yielded conflicting results.

Purpose of the Study:

• To investigate language lateralization in first-episode, medication-naive schizophrenia patients using functional MRI.
• To determine if reduced language lateralization is present at the earliest stages of schizophrenia.
• To explore the correlation between language lateralization and psychotic symptoms.

Main Methods:

• Functional MRI (fMRI) was employed to assess language lateralization.
• Thirty-five first-episode medication-naive schizophrenia patients and 43 healthy controls participated.
• Three language tasks (verb generation, antonym generation, semantic decision) were administered to calculate the Lateralization Index (LI) in seven language-related Regions of Interest (ROIs).

Main Results:

• Significantly reduced LI was observed in schizophrenia patients compared to controls across all ROIs (p<0.001).
• The most prominent reductions in LI were found in the inferior frontal gyrus (Broca's area) and superior temporal gyrus (Wernicke's area).
• No significant correlation was found between LI and positive symptoms (PANSS), hallucinations, or disorganization.

Conclusions:

• This study provides the first evidence of reduced language lateralization at the onset of schizophrenia, prior to medication.
• These findings indicate that abnormal language lateralization may be an early neurobiological marker of schizophrenia.
• The results suggest that reduced lateralization in early schizophrenia is not directly associated with positive psychotic symptoms.