A brief summary of TMS measures of cortical excitability and their relationship to neurotransmitters

TMS MeasureMEP (right anterior pollicis brevis response, following TMS to the left motor cortex)Neurochemistry InvolvedSelect References
Resting motor thresholdEmbedded ImageIon channels (voltage-gated Na+, AMPA glutamate)Ziemann and Rothwell (2000), Di Lazzaro et al. (2008)
Paired pulse facilitation (long interval facilitation, 15 ms)Embedded ImageGlutamate (AMPA, NMDA)Reis et al. (2008)
Paired pulse inhibition (short interval inhibition, 3 ms)Embedded ImageGABAaZiemann et al. (1996), Di Lazzaro et al. (2000a), Korchounov et al. (2005)
Cortical silent periodEmbedded ImageGABAb, dopamineZiemann et al. (1993)
Recruitment curve (dose–response curve)Embedded ImageCausal relationship between TMS input and MEP outputHanlon et al. (2015a)