Reliability of M1-P15 as a cortical marker for transcallosal inhibition: a preregistered TMS-EEG study

Abstract

Background: In a recently published study combining transcranial magnetic stimulation and electroencephalography (TMS-EEG), we provided first evidence of M1-P15, an early component of TMS-evoked potentials, as a measure of transcallosal inhibition between motor cortices. However, considering the technical challenges of TMS-EEG recordings, further evidence is needed before M1-P15 can be considered a reliable index. Objective: Here, we aimed at validating M1-P15 as a cortical index of transcallosal inhibition, by replicating previous findings on its relationship with the ipsilateral silent period (iSP) and with performance in bimanual coordination. Moreover, we aimed at inducing a task-dependent modulation of transcallosal inhibition. Methods: A new sample of 32 healthy right-handed participants underwent behavioral motor tasks and TMS-EEG recording, in which left and right M1 were stimulated during bimanual tasks and during an iSP paradigm. Hypotheses and methods were preregistered before data collection. Results: We successfully replicated our previous findings on the positive relationship between M1-P15 amplitude and the iSP normalized area. However, we did not confirm the relationship between M1-P15 latency and bimanual coordination. Finally, we show a task-dependent modulation of M1-P15 amplitude, which was affected by the characteristics of the bimanual task the participants were performing, but not by the contralateral hand activity during the iSP paradigm. Conclusions: The present results corroborate our previous findings in validating the M1-P15 as a reliable cortical marker of transcallosal inhibition, and provide novel evidence of its task-dependent modulation. Importantly, we demonstrate the feasibility of a preregistration approach in the TMS-EEG field to increase methodological rigor and transparency.

Investigating visuo-tactile mirror properties in Borderline Personality Disorder: a TMS-EEG study

“…Employing TMS during a task is known to enable the investigation of network-specific activity which is dependent on its functional status (Barchiesi et al, 2022; Jacquet & Avenanti, 2015; Silvanto, Muggleton, Cowey, & Walsh, 2007), while the simultaneous recording of EEG provides information on the spread of neural activation to brain areas effectively connected to the stimulated one (Bortoletto, Veniero, Thut, & Miniussi, 2015; Massimini et al, 2005; Zazio et al, 2021). Crucially, combining the two techniques in TMS-EEG recordings when participants are performing a task allows the investigation of brain connectivity in task-specific networks (Bortoletto et al, 2021; Morishima et al, 2009; Zazio et al, 2022). In both pw-BPD and HCs and in all conditions we successfully recorded clear TEPs components from S1 stimulation, namely N15, P60, N100, P200, P300, with topographical patterns overall similar to the ones described previously in HCs (Pisoni et al, 2018).…”

“…Thus, a sample of 20 HCs and 19 pw-BPD was left for ERP and TEP analysis. TMS-EEG data processing was performed in MATLAB R2020b (The Mathworks, Natick, MA, USA) with custom scripts using EEGLAB v.2020.0 (Delorme & Makeig, 2004) and FieldTrip functions (Oostenveld, Fries, Maris, & Schoffelen, 2011), and following the same steps applied in previous studies by our research group (Guidali, Zazio, et al, 2023;Zazio, Barchiesi, Ferrari, Marcantoni, & Bortoletto, 2022). Unless otherwise specified, the default parameters for the EEGLAB and FieldTrip functions were used.…”