Effects of Parkinson’s disease and dopamine on digit span measures of working memory

Abstract

Hospital, Bristol, UK, BS10 5NB. +44 (0)1174148186. John.grogan@bristol.ac.uk. 10 11 ACKNOWLEDGEMENTS 12 The authors thank BRACE for the use of their building, all the patients and 13 participants who took part in this research, and the funders (Wellcome [097081/Z/11/Z] and 14 Bristol Research into Alzheimer's and Care of the Elderly charity [BRI17/15]). 15 16 ABSTRACT 17 Rationale 18Parkinson's disease (PD) impairs working memory (WM) -the ability to maintain 19 items in memory for short periods of time and manipulate them. There is conflicting evidence 20 on the nature of the deficits caused by the disease, and the potential beneficial and 21 detrimental effects of dopaminergic medication on different WM processes. 22Objectives 23We hypothesised that PD impairs both maintenance and manipulation of items in WM 24 and dopaminergic medications improve this in PD patients but impair it in healthy older 25 adults. 26Methods 27 We tested 68 PD patients ON and OFF their dopaminergic medication, 83 healthy 28 age-matched controls, and 30 healthy older adults after placebo and levodopa administration. 29We used the digit span, a WM test with three components (forwards, backwards and sequence 30 recall) that differ in the amount of manipulation required. We analysed the maximum spans 31 and the percentage of lists correctly recalled, which probe capacity of WM and the accuracy 32 of the memory processes within this capacity, respectively. 33Results 34 PD patients had lower WM capacity across all three digit span components, but only 35 showed reduced percentage accuracy on the components requiring manipulation (backwards 36 and sequence spans). Dopaminergic medication did not affect performance in PD patients. In 37 healthy older adults, levodopa did not affect capacity, but did impair accuracy on one of the 38 manipulation components (sequence), without affecting the other (backwards). 39 Conclusions 40This suggests a non-dopaminergic deficit of maintenance capacity and manipulation 41 accuracy in PD patients, and a potential "overdosing" of intact manipulation mechanisms in 42 healthy older adults by levodopa. 43

Effect of cognitive and motor dual‐task on oropharyngeal swallowing in Parkinson's disease

“…This might be due to the older cohort with neurodegenerative disease, so that ‐ unlike in the healthy participants ‐ there was no further reserve to compensate the cognitive load of the concurrent task. In line with this hypothesis, previous studies have demonstrated that PD patients show impaired working memory capacity in the forward digit span task [41], which was used in the cognitive dual‐task paradigm. Also, PD patients might have to devote more cognitive attention to swallowing than healthy individuals.…”