Parkinson’s patients completed Digit Span Backward and Digit Span Forward ON and OFF medications, while healthy controls completed them once. We recruited 64 Parkinson’s disease patients and 22 age-and education-matched controls. Our study seeks to: (1) determine the validity of verbal Digit Spans for detecting cognitive impairment in Parkinson’s disease patients both ON and OFF medications and (2) ascertain the effects of dopaminergic medications on verbal Digit Span. Research indicates that the interaction between dopamine and working memory follows an Inverted-U shaped curve, but the effect of dopamine on Digit Span has not been well studied. Moreover, Digit Span Backward was recently validated as a screening tool for mild cognitive impairment in Parkinson’s disease when participants were medicated. Verbal digit span tasks offer a potentially straightforward and quick assessment of baseline working memory. It is therefore critical for movement disorders physicians to understand the potential dopaminergic effects on working memory when prescribing these medications. However, there is substantial evidence that dopamine also impacts cognition, in particular working memory. Although cognitive impairment is one of the strongest predictors of quality of life, dopaminergic anti-parkinsonian medications are designed to target motor symptoms. Parkinson’s disease patients are at an elevated risk of developing cognitive impairment.

Backward digit span cognitive control