Sleep specific alpha-activity indicates the progress of idiopathic Parkinson's disease

Objective: Deep brain stimulation (DBS) as a treatment option for various neurological disorders also allows to record local field potentials (LFP) from subcortical regions. Using coherence analysis between surface-EEG and LFPs from Globus pallidus in dystonia patients we recently characterized an alpha-activity in sleep stages N2 and N3 (Salih et al., 2009). Based on our findings we discussed whether this alpha-activity could act as a specific signature of the motor system in human non-REM sleep. Here we test whether patients with idiopathic Parkinson's disease (PD) show alterations of this alpha-activity. Methods: So far, nine PD patients were investigated (age: 44–71 years; m=5, f=4). DBS target was the subthalamic nucleus (STN). Coherence analysis was performed between surface-EEG and LFPs from STN using sequences for N2 and N3 in the frequency band between 0.5–40Hz. For all patients the Parkinson Disease Sleep Scale (PDSS), the Unified Parkinson Disease Rating Scale part III (UPDRS) and the clinical DBS outcome (i.e., improvement rate) were evaluated. Results: In 4 patients (44.4%) coherent alpha-activity was found between motor cortex and STN during non-REM sleep (N3>N2). These patients had lower UPDRS III scores compared to those patients who showed no alpha-activity (36.5 vs. 53.0). Mean PDSS scores were not different (113.5 vs. 111.0). Mean DBS outcome was 68% in patients with alpha-activity (vs. 62%). Discussion: The preliminary results of this study support the hypothesis that alpha-activity could be a signature of the motor system during non-REM sleep. The loss of alpha-activity in patients with higher UPDRS III scores indicates the physiologic nature of this activity as progressing neurodegeneration may lead to a decrease of non-REM specific alpha-activity.

Reference: Salih F, Sharott A, Khatami R, Trottenberg T, Schneider G, Kupsch A, Brown P, Grosse P. Functional connectivity between motor cortex and globus pallidus in human non-REM sleep. J Physiol (2009);587:1071–86.