title: The maximum-likelihood strategy for determining transcranial magnetic stimulation motor threshold, using parameter estimation by sequential testing is faster than conventional methods with similar precision.
abstract: BACKGROUND
  The resting motor threshold (rMT) is the basic unit of transcranial magnetic stimulation (TMS) dosing. Traditional methods of determining rMT involve finding a threshold of either visible movement or electromyography (EMG) motor-evoked potentials, commonly approached from above and below and then averaged. This time-consuming method typically uses many TMS pulses. Mathematical programs can efficiently determine a threshold by calculating the next intensity needed based on the prior results. Within our group of experienced TMS researchers, we sought to perform an illustrative study to compare one of these programs, the Maximum-Likelihood Strategy using Parameter Estimation by Sequential Testing (MLS-PEST) approach, to a modification of the traditional International Federation of Clinical Neurophysiology (IFCN) method for determining rMT in terms of the time and pulses required and the rMT value.
  
  
  METHODS
  One subject participated in the study. Five researchers determined the same subject's rMT on 4 separate days-twice using EMG and twice using visible movement. On each visit, researchers used both the MLS-PEST and the IFCN methods, in alternating order.
  
  
  RESULTS
  The MLS-PEST approach was significantly faster and used fewer pulses to estimate rMT. For EMG-determined rMT, MLS-PEST and IFCN derived similar rMT, whereas for visible movement MLS-PEST rMT was higher than for IFCN.
  
  
  CONCLUSIONS
  The MLS-PEST algorithm is a promising alternative to traditional, time-consuming methods for determining rMT. Because the EMG-PEST method is totally automated, it may prove useful in studies using rMT as a quickly changing variable, as well as in large-scale clinical trials. Further work with PEST is warranted.
authors.affiliation: Brain Stimulation Laboratory, Department of Psychiatry, Medical University of South Carolina, Charleston 29425, USA. mishory@musc.edu
authors.forename: Alexander
authors.initials: A
authors.lastname: Mishory
authors.forename: Christine
authors.initials: C
authors.lastname: Molnar
authors.forename: Jejo
authors.initials: J
authors.lastname: Koola
authors.forename: Xingbao
authors.initials: X
authors.lastname: Li
authors.forename: F Andrew
authors.initials: FA
authors.lastname: Kozel
authors.forename: Hugh
authors.initials: H
authors.lastname: Myrick
authors.forename: Zachary
authors.initials: Z
authors.lastname: Stroud
authors.forename: Ziad
authors.initials: Z
authors.lastname: Nahas
authors.forename: Mark S
authors.initials: MS
authors.lastname: George
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D004056:Differential Threshold; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D012984:Software; D050781:Transcranial Magnetic Stimulation