Motor Evoked Potential Amplitude in Motor Behavior-based Transcranial Direct Current Stimulation Studies: A Systematic Review.

Motor evoked potential amplitude (MEP) is frequently measured in transcranial direct current stimulation (tDCS) studies that target the primary motor cortex (M1), and a subset of these studies involve motor behavior. This systematic review explored the role of MEP as an indicator of neural change in M1-targeted tDCS studies involving motor behavior (i.e., motor practice and/or evaluation of motor performance) in healthy individuals, and examined the association between changes in motor performance and MEP. We executed our search strategy across four bibliographic databases. Twenty-two manuscripts met eligibility criteria. While anodal tDCS combined with motor practice frequently increased MEP, MEP outcomes did not necessarily align with changes in motor performance. Thus, MEP may not be the most appropriate indicator of neural change in tDCS studies that aim to improve motor performance.