PT  - JOURNAL ARTICLE
AU  - Melina Engelhardt
AU  - Darko Komnenić
AU  - Fabia Roth
AU  - Leona Kawelke
AU  - Carsten Finke
AU  - Thomas Picht
TI  - No impact of functional connectivity of the motor system on the resting motor threshold: A replication study
AID  - 10.1101/2020.10.26.354886
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2020.10.26.354886
4099  - http://biorxiv.org/content/early/2021/02/24/2020.10.26.354886.short
4100  - http://biorxiv.org/content/early/2021/02/24/2020.10.26.354886.full
AB  - The physiological mechanisms of corticospinal excitability and factors influencing its measurement with transcranial magnetic stimulation are still poorly understood. A recent study reported an impact of functional connectivity between the primary motor cortex and dorsal premotor cortex on the resting motor threshold of the dominant hemisphere. We aimed to replicate these findings in a larger sample of 38 healthy right-handed subjects with data from both hemispheres. Resting-state functional connectivity was assessed between the primary motor cortex and five a-priori defined motor-relevant regions on each hemisphere as well as interhemispherically between both primary motor cortices. Following the procedure by the original authors, we included age, the cortical grey matter volume and coil to cortex distance as further predictors in the analysis. We report replication models for the dominant hemisphere as well as an extension to data from both hemispheres and support the results with Bayes factors. Functional connectivity between the primary motor cortex and dorsal premotor cortex did not explain variability in the resting motor threshold and we obtained moderate evidence for the absence of this effect. In contrast, coil to cortex distance could be confirmed as an important predictor with strong evidence. These findings contradict the previously proposed effect, thus questioning the notion of the dorsal premotor cortex playing a major role in modifying corticospinal excitability.Competing Interest StatementThe authors have declared no competing interest.BFBayes factorCCDCoil-to-cortex distanceCIconfidence intervalFAfractional anisotropyFCfunctional connectivityM1primary motor cortexPMddorsal premotor cortexPMvventral premotor cortexRMTresting motor thresholdROIregion-of-interestrsfMRIresting-state functional magnetic resonance imagingSMAsupplementary motor areaS1primary somatosensory cortexTMStranscranial magnetic stimulation