Cognitive processing speed in older adults: relationship with white matter integrity

Area of Science:

• Neuroscience
• Gerontology
• Radiology

Background:

• Cognitive processing speed naturally declines with advancing age.
• White matter integrity is crucial for efficient neural communication.
• Diffusion Tensor Imaging (DTI) is a key MRI technique for assessing white matter microstructure.

Purpose of the Study:

• To investigate the relationship between white matter integrity and cognitive processing speed in healthy older adults.
• To identify specific white matter tracts critical for maintaining cognitive function with age.
• To determine if white matter integrity mediates age-related slowing of cognitive processing.

Main Methods:

• Cross-sectional study of 131 cognitively normal adults aged 55-87.
• Utilized a novel computerized, non-verbal, choice reaction time task battery.
• Performed Magnetic Resonance Imaging (MRI) with Diffusion Tensor Imaging (DTI) and tract-based spatial statistics.

Main Results:

• Reaction time significantly increased (slowed) with age.
• Lower fractional anisotropy (FA) in frontal and parietal white matter, particularly the anterior corpus callosum, correlated with slower reaction times.
• Key affected tracts included the genu and body of the corpus callosum, superior longitudinal fasciculus, and inferior fronto-occipital fasciculus.
• These associations were independent of gray/white matter atrophy and white matter lesion volume.

Conclusions:

• White matter integrity is a significant factor influencing cognitive processing speed in older adults.
• Reduced white matter integrity, especially in specific tracts, is associated with age-related cognitive slowing.
• Loss of white matter integrity statistically mediates the relationship between aging and decreased cognitive processing speed.