The symbol digit modalities test and the paced auditory serial addition test involve more than processing speed

Area of Science:

• Neuroscience
• Cognitive Psychology
• Clinical Neurology

Background:

• Slowed processing speed is a common cognitive deficit in multiple sclerosis (MS).
• Standard processing speed tests may involve other cognitive abilities beyond speed.
• Understanding these contributions is crucial for accurate cognitive assessment in MS.

Purpose of the Study:

• To determine the specific contributions of cognitive functions to performance on the Symbol Digit Modalities Test (SDMT) and Paced Auditory Serial Addition Test (PASAT).
• To investigate how processing speed, working memory, and learning interact in MS patients and controls on these tests.

Main Methods:

• Adults with relapsing-remitting MS (n=70) and controls (n=72) were assessed.
• Participants completed the SDMT, PASAT, and measures of processing speed, working memory, and learning.
• Hierarchical regression analyses examined the contributions of various cognitive factors and their interactions.

Main Results:

• Processing speed and working memory influenced both SDMT and PASAT performance.
• Learning also contributed to SDMT performance.
• Interactions showed processing speed's importance varied with working memory capacity and MS status.

Conclusions:

• The SDMT and PASAT are multifactorial measures.
• These tests are useful for screening cognitive decline in MS.
• They do not isolate specific cognitive functions, limiting precise diagnosis of deficits.