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Description: Transcranial magnetic stimulation (TMS)-electroencephalography coregistration (TMS-EEG) is a promising technique to measure effective connectivity, i.e., the directed transmission of physiological signals along cortico-cortical tracts. Indeed, the activation induced by the TMS pulse in the target region travels to distant connected areas along white matter tracts, generating TMS-evoked potentials (TEPs). A crucial point to be addressed for developing connectivity biomarkers from TEPs is how they are affected by changes in stimulation parameters, such as pulse waveform and the direction of the induced current. Different stimulation parameters across studies may impact latency or amplitude of responses, contributing to the general variability in TMS-EEG findings. To date, the impact of TMS parameters on responses generated in cerebral cortico-cortical pathways has been poorly investigated. To deepen this investigation, we will use as an operative model the M1-P15, an early TEP component reflecting the interhemispheric inhibition of motor areas contralateral to TMS via the corpus callosum. Assuming that the M1-P15 can be recorded regardless of TMS parameters, namely, the direction of the induced current in the brain – anterior-posterior, posterior-anterior, latero-medial – and the TMS pulse waveform – monophasic, biphasic, we will investigate whether these modulations influence M1-P15 latency and amplitude. We will also test M1-P15 reproducibility across our experimental conditions using the concordance and intraclass correlation coefficients. Finally, resting motor threshold and motor-evoked potentials will be collected in every experimental condition as control variables, allowing us to deepen the possible relationship between cortico-spinal and cortico-cortical pathways that different stimulator parameters may activate within the motor system.