Visual and motor confounds on the symbol digit modalities test

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Slowed information processing speed is a primary cognitive deficit in multiple sclerosis (MS).
• The Symbol Digit Modalities Test (SDMT) is the standard measure for processing speed in MS.
• SDMT performance is influenced by visual, oculomotor, and oralmotor deficits common in MS.

Purpose of the Study:

• To investigate the relationship between the King-Devick Test (KDT) and the SDMT in individuals with MS.
• To determine the extent to which KDT performance, reflecting oculomotor and oralmotor skills, contributes to SDMT scores.

Main Methods:

• One hundred and thirty participants with MS completed the oral version of the SDMT and the KDT.
• Nonparametric bootstrapped regression models with 1000 samples were used to analyze the data.
• Bias-corrected confidence intervals were calculated.

Main Results:

• King-Devick Test (KDT) performance accounted for 31% of the variance in SDMT performance.
• This correlation between KDT and SDMT was moderate and significantly greater than demographic (0.7%) and disease-related (10%) variables.
• Bootstrapped confidence intervals for KDT's contribution were 18% - 43%.

Conclusions:

• Visual, oralmotor, and oculomotor functions are significant contributors to SDMT performance in MS.
• These sensory and motor components must be considered when interpreting SDMT results in MS patients.
• The KDT offers valuable insights into the motor and visual demands affecting cognitive assessments in MS.