Information processing speed mediates the relationship between white matter and general intelligence in schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Schizophrenia is increasingly viewed as a disorder of brain connectivity rather than localized deficits.
• White matter abnormalities are hypothesized as the structural basis for this proposed dysconnectivity.
• Information processing speed is crucial for higher-order cognition, but its link to white matter and intelligence in schizophrenia is unclear.

Purpose of the Study:

• To investigate the relationship between white matter structure and general intelligence in schizophrenia.
• To test the hypothesis that processing speed mediates the association between white matter integrity and general intelligence.

Main Methods:

• Tract-based Spatial Statistics (TBSS) was used to analyze white matter diffusion parameters in 46 regions-of-interest (ROIs).
• Principal component analysis (PCA) extracted general factors for white matter structure (gFA, gMD), general intelligence (g), and processing speed (gspeed).
• Correlational and mediation analyses were performed on these extracted factors.

Main Results:

• A significant positive correlation was observed between general intelligence (g) and general white matter fractional anisotropy (gFA) (r=0.67, p=0.001).
• Processing speed (gspeed) partially and significantly mediated this relationship (56.22% CI: 0.10-0.62).
• These findings support a model where white matter integrity underpins general intelligence, with processing speed playing a partial mediating role.

Conclusions:

• White matter structure may serve as a neuroanatomical substrate for general intelligence in schizophrenia.
• Information processing speed is a key cognitive factor that partially mediates the relationship between white matter integrity and general intelligence.
• This study provides a plausible model for structure-function relationships in schizophrenia, highlighting the interplay between white matter, processing speed, and intelligence.