The Attention Demands of Movements

The probe technique has been employed extensively to measure the attention demands of movement control. Inherent in any RT paradigm is the potential confounding effect of anticipation. Experiment 1 studied this problem by varying probe frequency (or, conversely, catch-trial frequency) for three independent groups of subjects performing the same movement. Probe frequencies of one-third and two-thirds produced V-shaped curves of probe RT plotted against probe position within the movement, while a three-thirds condition was described by a negatively sloped linear function. Because of the different shaped curves it was recommended that a two-thirds frequency be adopted by all researchers in this area. Experiments 2 and 3 looked at the effects of movement length and movement time on the attention demands of movement. Shorter (11-cm) movements were more attention demanding in the middle of the movement than the longer (50-cm) movements, but movement time had no effect.     

The effects of clinical motor variables and medication dosage on working memory in Parkinson’s disease

In this study, we investigate the interrelationship between clinical variables and working memory (WM) in Parkinson’s disease (PD). Specifically, the aim of the study was to investigate the relationship between disease duration, dopaminergic medication dosage, and motor disability (UPDRS score) with WM in individuals with PD. Accordingly, we recruited three groups of subjects: unmedicated PD patients, medicated PD patients, and healthy controls. All subjects were tested on three WM tasks: short-delay WM, long-delay WM, and the n-back task. Further, PD encompasses a spectrum that can be classified either into akinesia/rigidity or resting tremor as the predominant motor presentation of the disease. In addition to studying medication effects, we tested WM performance in tremor-dominant and akinesia-dominant patients. We further correlated WM performance with disease duration and medication dosage. We found no difference between medicated and unmedicated patients in the short-delay WM task, but medicated patients outperformed unmedicated patients in the long-delay WM and n-back tasks. Interestingly, we also found that akinesia-dominant patients were more impaired than tremor-dominant patients at various WM measures, which is in agreement with prior studies of the relationship between akinesia symptom and basal ganglia dysfunction. Moreover, the results show that disease duration inversely correlates with more demanding WM tasks (long-delay WM and n-back tasks), but medication dosage positively correlates with demanding WM performance. In sum, our results show that WM impairment in PD patients depend on cognitive domain (simple vs. demanding WM task), subtype of PD patients (tremor- vs. akinesia-dominant), as well as disease duration and medication dosage. Our results have implications for the interrelationship between motor and cognitive processes in PD, and for understanding the role of cognitive training in treating motor symptoms in PD.