Slowing of high-speed memory scanning in Parkinson's disease is related to the severity of parkinsonian motor symptoms

High-speed memory scanning (Sternberg paradigm) was tested in a collective of 20 parkinsonian patients (10 newly diagnosed, untreated patients, duration of the disease 0.5–3.8, mean 1.5 years; 10 levodopa-treated patients, duration of the disease 4.2 to 11, mean 7.6 years). The levodopa-treated patients stopped taking levodopa before the test. There was a tendency towards retarded memory scanning in the patients' collective compared with 20 healthy controls with similar ages and verbal IQs (p=0.076, Mann-Whitney U test). The mental slowing correlated significantly with bradykinesia and the sum-score of the Columbia University Parkinson Rating Scale (p=0.021 and 0.019; Spearman rank correlation). Kruskal-Wallis ANOVA revealed a significant mental slowing in the subgroup of patients with Parkinson's disease for >4 years compared with the newly diagnosed patients and the controls (H=8.54; p=0.019 and 0.006, Mann-Whitney U test). The findings suggest a mental slowing in Parkinson's disease, which is associated with the progression of parkinsonian motor symptoms and not with depression.