Consistency of MEPs elicited at two TMS intensities

Abstract Background: The mechanisms of cortico-motor plasticity can be evaluated in human motor cortex by comparing the amplitude evoked potentials (MEPs) elicited single-pulse transcranial magnetic stimulation (spTMS) after a repetitive (rTMS) regimen. Post-rTMS increases/decreases MEPs are interpreted as long-term potentiation-/depression-like changes, respectively. Objective: To compare two most common spTMS intensities—120% resting threshold (120%RMT) and intensity to elicit an average ∼1mV MEP (1mV-MEP)—on within-session between-sessions consistency MEPs. Methods: Seven healthy adults (21-70 years; 5 males) consented participate this ongoing IRB-approved study. Participants completed identical sessions (test-retest; ≥1 day apart), each consisting four blocks 120 neuronavigated trials. Blocks 1-2 were administered using either 120%RMT or 1mV-MEP (counterbalanced) separated 15 minutes where participants remained seated (simulating rTMS). After 20-minute break could move around, 3-4 at other with same 15-minute rest break. Results: PRE refers 1+3 POST 2+4. Data mean±SD. In Test-visit, (mV) 1.4±0.5 (PRE) 1.5±0.5 (POST) for 2.6±2.1 2.0±2.0 120%RMT. Retest-visit, 1.4±0.7 1.3±0.6 1.8±1.5 1.7±1.2 percent change (%Δ) from was 15.2±38.5 (Test-visit) 4.9±45.5 (Retest-visit) -29.2±21.3 (Test) 5.2±42.4 %Δ Test-visit 4.1±41.1 32.6±149.1 Conclusions: Compared 120%RMT, show lower inter-individual variance smaller changes between sessions. These results suggest is better suited index induced rTMS. Research Category Technology Methods Basic Research: 10. Transcranial Magnetic Stimulation (TMS) Keywords: stimulation, potentials, variability,