Development of a Conversion Equation for Active Motor Threshold for the Magstim Bistim Transcranial Magnetic Stimulation Unit

Purpose: The purpose of this study is to establish whether or not there is a significant difference between the stimulus outputs of the top and bottom units of the Magstim Bistim. A second objective is to develop a conversion equation for the Active Motor Thresholds (AMTs) collected by the two units. Methods: Fourteen subjects (8 women,6 men,n=14,age=21.5±1.4 years,height=168.5±9.767 centimeters,weight=72.5±13.4 kilograms) were recruited for this study. For each subject, AMT was measured from both Unit 1 and Unit 2 of the Magstim Bistim. AMT was measured on the area of the motor cortex that showed the strongest response from the Vastus Medialis Oblique. Results: A paired samples t-test and a Pearson-product moment analysis showed that there was a significant difference between Units 1 and 2 and that there was a strong, positive correlation between these two variables (t(13)=-6.69,P<0.001; r=0.81,P