Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique to induce longer lasting plasticity changes in the brain. Applied with lower frequency of about 1 Hz, it is considered to evoke inhibitory cortical effects, whereas with higher frequencies it can cause facilitatory effects. Other rTMS procedures with patterned and combined administration methods are also categorized according to their effects on cortical excitability. With single transcranial magnetic stimulation (TMS) pulses, derivations of cortical excitability, such as transcranial evoked potentials (TEPs), and of cortico-spinal excitability, such as motor evoked potentials (MEPs), can measure rTMS effects. Since high variability is associated with both TMS and rTMS measures, the present dissertation investigates rTMS effects and test-retest reliability along with influencing variables, such as the current direction induced in the brain during TMS pulse application. Three studies pursue the detailed examination of firstly, the effects and reliability of 1 and 20 Hz rTMS on MEPs, secondly, the effects and reliability of MEPs of previously published rTMS articles, and thirdly, the influence of current direction on TEPs and MEPs in a 1 Hz rTMS protocol. The first study revealed that neither inhibitory nor facilitatory effects were replicable, although there was descriptive tendency within the data. The reliability of both the 1 and 20 Hz rTMS protocol was low to moderate. The second study showed an overall low to moderate reliability of rTMS protocols with only two out of 15 articles showing high reliability, whereby no influences of factors inducing variability or publication bias was found. The third study further highlighted the lack of repeatability of rTMS effects by resulting in contrary effects for 1 Hz rTMS. Both MEP and TEP components were influenced by current direction. This dissertation emphasizes the variability in TMS and rTMS and calls upon improvement of application, data acquisition and preprocessing to increase both rTMS effects and reliability.     «

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique to induce longer lasting plasticity changes in the brain. Applied with lower frequency of about 1 Hz, it is considered to evoke inhibitory cortical effects, whereas with higher frequencies it can cause facilitatory effects. Other rTMS procedures with patterned and combined administration methods are also categorized according to their effects on cortical excitability. With single transcranial magnetic stimulation (TM...     »