Levodopa increases functional connectivity in the cerebellum and brainstem in Parkinson’s disease

Abstract

ARTICLE Sir, we would like to comment on a recent article published in Brain by Hacker et al. (2012), which reported functional connectivity alteration in 13 patients with Parkinson’s disease in the medicated state compared with healthy control subjects. Although the authors showed very interesting results, they could not disentangle the effects of levodopa within the patient group. We investigated the influence of dopaminergic medication on patients with Parkinson’s disease in an intra-individual design based on functional connectivity derived from resting state functional MRI. We used a model-free and data-driven approach with eigenvector centrality mapping (Lohmann et al. , 2010)—an algorithm similar to Google’s PageRank routine. The method automatically detects all brain areas serving as communication hubs, which—unlike other areas—have greater connectivity with many other parts of the brain. Hence, as distinct from previously used methods, this approach is unbiased by manual selection of the seed regions and thereby independent of the expert’s decision. Using the eigenvector centrality analysis we found, concurrently with Hacker et al. (2012), …