S147. Effect of 1 Hz and 5 Hz rTMS over supplementary motor area on motor cortical excitability

Introduction Recent clinical trial of repetitive transcranial magnetic stimulation (rTMS) in Parkinson’s disease (PD) showed that both 1 Hz and 5 Hz rTMS over supplementary motor cortex (SMA) are effective for motor symptoms in PD. Previous studies have also indicated 1 Hz rTMS over primary motor cortex (M1) induces an inhibition whereas 5 Hz rTMS produce facilitation in excitability. Our aim is to clarify why both 1 Hz and 5 Hz rTMS, which have the opposite effects in cortical excitability, show the similar beneficial effects for PD. Recent clinical trial of repe. Methods Subjects are twelve right-handed healthy volunteers (10 men, mean age 30.9 ± 6.5 years). rTMS consists of total 1000 pulses of 1 Hz, 5 Hz rTMS and realistic sham stimulation over SMA at intensity of 110% active motor threshold for the tibialis anterior (TA). We recorded motor-evoked potentials (MEP) from the right first dorsal interosseous (FDI) muscle and measured MEPs, short-intercortical inhibition (SICI) and intercortical facilitation (ICF) before, immediately (0), 15 and 30 min after the end of each condition. Results A two-way repeated measures ANOVA demonstrated a significant main effect of ‘condition’ (1 Hz, 5 Hz and sham) on the mean MEP amplitude ( F 2,87  = 4.72, P  = 0.0113), whereas no significant effect on ‘time’ (T0-T30) ( F 2,87  = 0.589, P  = 0.56) and ‘time’ × ‘condition’ interaction (F 2,87 =0.79. P = 0.535). Post hoc t tests revealed that decrease in MEP amplitude lasted at least for 15 min after the end of stimulation (0 min P  = 0.0048; 15 min P  = 0.0047). SICI and ICF did not show significant changes after 1 Hz rTMS. There were no significant changes either in MEP, SICI and ICF after 5 Hz rTMS and sham stimulation. Conclusion 1 Hz SMA-rTMS decreased the amplitude of MEP evoked by a single-pulse TMS, whereas 5 Hz SMA-rTMS did not show significant changes. We suggest that 1 Hz and 5 Hz SMA-rTMS show different physiological after-effects, even though both conditions have a similar therapeutic effect for PD. It is presumable that these two rTMS have different mechanism for improving motor symptoms of PD. Further investigation is required to clarify the precise physiological effects of SMA-rTMS.