Entrainment of movement-related brain oscillations to improve symptoms in Tourette syndrome

Abstract

Tics in Tourette syndrome are associated with changes in the synchrony of movement-related brain oscillations within the sensorimotor cortex, which are associated with cortical hyperexcitability. Non-invasive brain stimulation can be used to modulate excitability of the motor cortex and techniques such as repetitive transcranial magnetic stimulation (TMS) have been shown to be effective in reducing the frequency of tics. However cortical methods such as TMS are difficult to administer outside of the clinic, whereas if a method could be developed using peripheral stimulation, then it would be possible for patients to safely deliver this intervention at home. The delivery of rhythmic pulses of stimulation has shown frequency and region-specific entrainment of brain oscillations, and when delivered at frequencies associated with movement inhibition, entrainment can cause slowing of movement responses. Here, we summarize evidence that rhythmic median nerve stimulation (MNS) can be used to entrain movement-related brain oscillations. Entrainment of these oscillations reduces both tic frequency and the urge-to-tic in Tourette syndrome patients. Furthermore, the stimulation does not impair the execution of voluntary movement or cognitive performance, indicating the potential for rhythmic MNS to be used as a therapy in disorders associated with sensorimotor hyperexcitability.