Cerebellar contribution to gait and postural control: an rTMS study

The cerebellum performs similar tasks for cognitive functions as it does for motor control; however, cerebellar deficits following a lesion typically overlap symptoms, making it challenging to determine the precise role of the cerebellum on sensorimotor activities. This study aims to reproduce a virtual lesion with TMS, to explore the specific role of the cerebellum in this domain (sensorimotor) and identify specific parameters that can be applied in clinical practice. Fifteen healthy participants were assigned cerebellar stimulation. A sham stimulation for 15 minutes and 1Hz repetitive-Transcranial Magnetic Stimulation for 20 minutes were delivered over the cerebellum. Subsequently, participants encountered different tasks such as balance, walking, and distance estimation, wearing eight inertial measurement units. All tasks were performed with eyes open (EO), and eyes closed (EC) after sham and real stimulation. Results show that after cerebellar inhibition, we have increased instability in both real and sham stimulation. The cerebellar instability increased in both EO and EC (path length trajectory of the center of mass). Afterwards, values increased after real stimulation in comparison to the sham, but only with the EC; within the walking task, the range of motion after real stimulation increased. Additionally, the three gait temporal parameters that showed a significant increase are stride and length only with EC, speed variability, and step width. Lastly, the kinematic variability of the ankle and knee also increased in the real stimulation with EC. There was an increase in variability in the ankle angle, also in the elevation of foot and knee angle, and an increase in average ankle angle. Regarding the body schema measured by the distance estimation task, the cerebellar inhibition seems not to be involved. In summary, the study proves the involvement of cerebellum in sensory motor related function, specifically by the observed variables. These findings can be a useful tool in clinical practice to speed up the diagnosis of cerebellar impairment and to improve treatments.