Reduction of Continuous Theta Burst Stimulation-Induced Motor Plasticity in Healthy Elderly With COMT Val158Met Polymorphism

OBJECTIVE: To delineate whether cortical plasticity induced by continuous theta burst stimulation (cTBS) differed according to catechol-O-methyltransferase (COMT) gene polymorphism in healthy older adults. METHODS: Eighteen healthy older volunteers (mean age 73.78±5.04; 12 females and 6 males) were recruited. Volunteers randomly assigned in either a sham-first or real cTBS first group participated in two separate TMS visits with at least a 2-day wash-out period. Genotyping was carried out at baseline by a separate researcher who was blinded. cTBS was delivered in a hot spot over M1 at an active motor threshold of 80%. Motor evoked potentials (MEPs) were obtained at 120% of the resting motor threshold before and after sham/cTBS. RESULTS: The relative MEP to baseline was significantly decreased 0 and 10 minutes post-stimulation and increased 40 minutes post-stimulation, as compared with the sham condition. Immediately after cTBS, the Val/Val group had a significantly reduced relative MEP value, as compared with the MET carrier group. CONCLUSION: In healthy older persons, cTBS-induced motor plasticity was reduced in the COMT Val/Val group as compared with the (158)Met carrier group.