Effects of Cerebellar Transcranial Direct Current Stimulation on Cerebellar Brain Inhibition as a Function of TMS Coil Orientation.

INTRODUCTION

Cerebellar brain inhibition (CBI) is a way to quantify the cerebellar influence on the motor cortex in humans. Studies suggest that the orientation of the transcranial magnetic stimulation (TMS) coil influences which motor networks are activated. This study investigated the influence of cerebellar transcranial direct current stimulation (ctDCS) on CBI as a function of coil orientation (anterior-posterior [AP] vs. posterior-anterior [PA]). An interstimulus interval (ISI) of 7 ms (CBI-AP-7) was used for AP orientation and 5 ms (CBI-PA-5) for PA orientation.

METHODS

Young and healthy participants received anodal, cathodal, or sham ctDCS treatment for 15 min on three different days. On each day, CBI was determined for both coil positions immediately after and 30, 60, and 120 min after ctDCS application.

RESULTS

For CBI-PA-5, no significant ctDCS effect was detected. For CBI-AP-7, there was an increase in CBI by anodal ctDCS and a decrease in CBI by cathodal ctDCS, although the latter did not reach statistical significance.

CONCLUSION

Findings provide further support that different cerebello-cerebral motor networks may be activated in CBI-AP-7 and CBI-PA-5, with only CBI-AP-7 being significantly affected by ctDCS. CBI-AP-7 may be a more sensitive tool for investigating CBI effects than the CBI-PA-5 procedure, which is most commonly used.