Preservation of explicit learning of visuomotor sequences during Parkinson's disease progression

While motor learning approaches are effective in rehabilitating Parkinson's disease (PD) patients, many studies reported deficits in sequential motor learning in these patients. We hypothesised that preserved explicit learning of visuomotor sequences in PD patients contributed to the effectiveness of motor learning approaches. However, there are very few studies analysing explicit learning of visuomotor sequences during the progression of PD. We investigated this phenomenon in 23 patients with moderate to severe PD (Hoehn-Yahr stages II-IV) and 17 age-matched controls using sequential button-press tasks (2 × 5 task). We found (1) no significant differences in numbers of errors in the 2 × 5 task among control and PD groups. (2) There was a significant difference in response times while exploring correct sequences (ERT) among control and PD groups; ERTs in stage-IV patients tended to be longer than those of control and stage-II groups. (3) All four groups significantly improved their performance (i.e., reduced ERTs in the 2 × 5 task) with sequence repetition, although stage-III:IV patients were slower. Thus, even patients with severe PD can learn visual sequences and can translate them into visuomotor sequences (explicit visuomotor sequence learning), albeit slower than controls, providing evidence for effective motor learning approaches during rehabilitation of patients with advanced PD.