Limited evidence for validity and reliability of non-navigated low and high frequency rTMS over the motor cortex

Abstract

The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) are often described as inhibiting for low frequency and facilitating for high frequency protocols, leading to the lofi-hife heuristic. However, the data basis for this is inconsistent and reliability of rTMS is barely evaluated. The present study examines the validity of this lofi-hife heuristic at group and single subject level and the reliability of rTMS in a non-navigated setting close to clinical application. In 30 healthy participants, 1 Hz and 20 Hz rTMS were each administered twice over the left motor cortex resulting in four sessions/participant. Motor evoked potentials (MEPs) were measured before and after each session. Reliability measures were intraclass and Pearson's correlation coefficient (ICC and r). The heuristic was not evident at group level. At single-subject level four participants responded with heuristic-conform changes, i.e., concomitant decreases for 1 Hz and increases for 20 Hz sessions. ICCs and r were low to moderate. Within subgroups of less confounded measures, we found good r values for 20 Hz rTMS. Results demonstrate high inter- and intraindividual variability of rTMS questioning the lofi-hife heuristic. Methodological improvements for the usage of rTMS might help to increase validity and reliability of non-invasive brain stimulation.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

Author SS received funding from the European Union's Horizon 2020 Framework Programme (grant agreement number 848261, UNITI project) and CK, MO and SS received funding from dtec.bw - Digitalization and Technology Research Center of the Bundeswehr (MEXT project).

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics committee of the University of Regensburg gave ethical approval for this work. (ethical approval number: 16-101-0305)

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Data Availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author (CK) on reasonable request.

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