P67. Effects of static magnetic fields on the human motorcortex. Issue 8 (August 2015)

• Record Type: Journal Article
• Authors: Kufner, M.; Brückner, S.; Kammer, T.
• Is Part Of: Clinical neurophysiology. Volume 126:Issue 8(2015:Aug.)
• Page Start: e128
• Page End: e129
• Publication Date: 2015-08
• Subjects: Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2015.04.201
• Languages: English
• ISSNs: 1388-2457

Abstract

<abstract xml:lang="en" abstract-type="author" id="ab005"> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <p id="sp005">Transcranial static magnetic field stimulation (tSMS) has been introduced as an easy applicable, non-invasive neurostimulation technique with no side-effects like pain, discomfort or risks of seizures. Up to now, the two studies applying tSMS to the human motor cortex (Oliviero et al., 2011; Silbert et al., 2013) showed inhibitory effects on cortical excitability. In both experiments, decreased motor evoked potentials (MEPs) for a time period lasting 3–6 min following stimulation were reported.</p> <p id="sp010">In our study we aimed to replicate the results in the motor system.</p> <p id="sp015">Twelve healthy, right-handed subjects (5 men, mean age 22.9 years) participated in the study. Motor cortex excitability was measured using single- pulse transcranial magnetic stimulation (TMS) before and after a 15 min period of tSMS application.</p> <p id="sp020">Surface electromyography (EMG) was recorded from the right first dorsal interosseous (FDI). First, a coil position was defined on the left M1 to evoke the largest MEP. Then, a TMS intensity was defined to elicit MEPs of about 1 mV. As a baseline measurement, 100 MEPs were recorded with an interval of 5–8 s between pulses, covering about 12 min. For tSMS, a cylindrical Neodym magnet of 30 mm height and 45 mm diameter (150 mT at 2 cm distance) was held over the left M1 for 15 min. During stimulation, participants performed an acoustic oddball task to standardize brain activity. Following tSMS, 100 MEPs were recorded to evaluate possible long-lasting after-effects. Pre- and post-stimulation pulses were grouped together in blocks of 2 min each. Time point post1 started 2 min after SMS application.</p> <p id="sp025">Data were subjected to an rmANOVA with the within factors STIMULATION (pre, post) and TIME (1, 2, 3, 4, 5, 6). There was a main effect of the factor TIME (<italic>F</italic><sub>5, 55</sub> = 2.56, <italic>p</italic> < 0.04), but no effect of the factor STIMULATION and no interaction. Post hoc Fisher's LSD revealed at time points 4 and 5 a significant increase in MEP amplitude irrespective of tSMS. Adding the covariate SEX to the rmANOVA, the interaction TIME x SEX was also significant (<italic>F</italic><sub>5, 50</sub> = 3.84, <italic>p</italic> < 0.006). Post hoc analysis showed that the detected increase in MEP amplitude was only present in male subjects.</p> <p id="sp030">The expected inhibitory effect of the stimulation could not be shown in our experiment. We found an unspecific increase in MEP amplitude of male subjects after about 50 single pulses (8 min) that occurred both in the control measurement (pre) as well as after tSMS exposure. We are planning to replicate both aspects of the present study in order to clarify the postulated tSMS effect as well as the observed sex-specific MEP increase over time.</p> </sec> </abstract>