Fast estimation of transcranial magnetic stimulation motor threshold.

BACKGROUND In Transcranial Magnetic Stimulation (TMS), the Motor Threshold (MT) is the minimum intensity required to evoke a liminal response in the target muscle. Because the MT reflects cortical excitability, the TMS intensity needs to be adjusted according to the subject's MT at the beginning of every TMS session. OBJECTIVE Shorten the MT estimation process compared to existing methods without compromising accuracy. METHODS We propose a Bayesian adaptive method for MT determination that incorporates prior MT knowledge and uses a stopping criterion based on estimation of MT precision. We compared the number of TMS pulses required with this new method with existing MT determination methods. RESULTS The proposed method achieved the accuracy of existing methods with as few as seven TMS pulses on average when using a common prior and three TMS pulses on average when using subject-specific priors. CONCLUSIONS Our adaptive Bayesian method is effective in reducing the number of pulses to estimate the MT.