Cortical response to proprioceptive stimulation in primary orthostatic tremor – a magnetoencephalography study

• This is the first study to investigate cortical activation in response to proprioceptive stimulation in orthostatic tremor. • Passive movements of the finger and foot were induced using custom-made MEG-compatible pneumatic movement actuators. • We found no difference in event-related desynchronization or subsequent synchronization between patients and controls. Patients with primary orthostatic tremor (OT) are affected by a strong feeling of instability. Our aim was to investigate whether cortical response to proprioceptive information is altered in OT compared with healthy control subjects (HC) using magnetoencephalography (MEG). Fifteen OT patients and 15 HCs were examined using whole-head MEG. Proprioceptive stimulation was evoked by passive movements of the right index finger and right foot. Time-frequency responses were extracted in the frequency range of 8–30 Hz. The MEG sensor with the highest amplitude change time-locked to the proprioceptive stimulus was used to calculate the amplitude of event-related desynchronization (ERD) and subsequent event-related re-synchronization (ERS). Finger stimulation induced reliable ERD and ERS, as expected, in both OT patients and HC. Foot stimulation induced weaker ERS in both groups. Cluster-based permutation tests did not reveal any significant differences between the OT and HC groups. We did not find evidence supporting a generally altered cortical response to proprioceptive stimulation in patients with OT. This is the first study on proprioceptive cortical processing in OT. The results do not support the interpretation that the characteristic intense feeling of instability in OT is linked to altered cortical response to proprioceptive information.