Composite reaction time and variability correlate with whole-brain white-matter characteristics

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuroimaging

Background:

• Processing speed and brain network characteristics are linked, but findings are inconsistent.
• Previous studies faced limitations due to task variations, behavioral measures, and specific white-matter tracts.

Purpose of the Study:

• To clarify the relationship between individual differences in cognitive speed and white-matter brain networks.
• To address inconsistencies in prior research using advanced neuroimaging and modeling techniques.

Main Methods:

• Utilized a large dataset (N=159) with high-gradient 3T Connectom MRI data.
• Combined data from three reaction-time tasks for composite cognitive performance measures.
• Applied the drift-diffusion model to derive processing speed parameters (drift rate, boundary separation, non-decision time).
• Explored relationships between behavioral parameters and structural brain networks (streamline counts, myelin water fraction) using general linear models.

Main Results:

• Found small, negative associations between global network efficiency and both mean reaction time and reaction-time variability.
• These effects were not consistently captured by drift-diffusion model parameters.
• The association with reaction-time variability was robust to age, while age significantly influenced the mean reaction time association.

Conclusions:

• Structural brain organization shows a small association with cognitive processing speed, particularly reaction-time variability.
• Age-related physiological changes may be key to understanding structure-function relationships in cognitive speed.
• The findings highlight the complexity of brain-behavior correlations and suggest caution in interpreting drift-diffusion model parameters.