A user-friendly input-output (IO) curve analysis tool for variable brain stimulation responses, particularly evoked potentials in transcranial magnetic stimulation (TMS)

BackgroundMotor-evoked potentials (MEPs) are among the few readily observable direct responses to suprathreshold stimuli administered to the brain. They serve for a variety of applications, often in the form of dose-response curves, also called recruitment or input-output (IO) curves. However, MEPs and thus IO curves demonstrate extreme trial-to-trial variability that can exceed more than two decimal orders of magnitude. Recent studies have identified issues in previous statistical analysis of IO curves and introduced better methods, others could quantitatively separate several widely independent variability sources. However, research has failed providing the field with a user-friendly implementation of the methods for analysing such IO curves statistically sound and separating variability so that they were limited to a few research groups. ObjectiveThis work intends to provide the latest methods for analysing IO curves and extract variability information in an open-source package so that the community can easily use and adapt them to their own needs. MethodsWe implemented recent IO curve methods with a graphical user interface and provided the code as well as compiled versions for Mac, Linux, and Windows. ResultsThe application imports typical IO data of individual stimulus-response sets, guides users step by step through the analysis, and allows exporting of the results including figures for post-hoc analysis and documentation. ConclusionThis graphical application offers a user-friendly environment for analysing the variability of evoked potentials and its various contributions, catering to the needs of clinical and experimental neuroscientists.