Occipital repetitive transcranial magnetic stimulation does not affect multifocal visual evoked potentials
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RESEARCH ARTICLE
BMC Neuroscience Open Access
Occipital repetitive transcranial magnetic stimulation does not affect multifocal visual evoked potentials Robert Kolbe1†, Aykut Aytulun1†, Ann‑Kristin Müller1, Marius Ringelstein1, Orhan Aktas1, Alfons Schnitzler1,2, Hans‑Peter Hartung1, Stefan Jun Groiss1,2 and Philipp Albrecht1*
Abstract Background: To identify mechanisms of cortical plasticity of the visual cortex and to quantify their significance, sensitive parameters are warranted. In this context, multifocal visual evoked potentials (mfVEPs) can make a valuable contribution as they are not associated with cancellation artifacts and include also the peripheral visual field. Objective: To investigate if occipital repetitive transcranial magnetic stimulation (rTMS) can induce mfVEP changes. Methods: 18 healthy participants were included in a single-blind crossover-study receiving sessions of excitatory, occipital 10 Hz rTMS and sham stimulation. MfVEP was performed before and after each rTMS session and changes in amplitude and latency between both sessions were compared using generalized estimation equation models. Results: There was no significant difference in amplitude or latency between verum and sham group. Conclusion: We conclude that occipital 10 Hz rTMS has no effect on mfVEP measures, which is in line with previous studies using full field VEP. Keywords: Multifocal visual evoked potentials, Repetitive transcranial magnetic stimulation, Occipital stimulation, Excitatory stimulation, Long term potentiation, Cortical plasticity Background The procedure of repetitive transcranial magnetic stimulation (rTMS) uses a strong magnetic field generated by a coil placed on the skull to induce an electric current in the upper layer of the cortex [1]. While single magnetic field pulses can be used to stimulate the cortical area, repetitive pulses can modify the excitability in an excitatory or inhibitory manner. In general, higher frequencies than 5 Hz [2] have a facilitating effect while lower frequencies around 1 Hz are considered inhibitory [3].
*Correspondence: [email protected] † Robert Kolbe and Aykut Aytulun contributed equally to this work 1 Department of Neurology, Medical Faculty, Heinrich-Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany Full list of author information is available at the end of the article
The direct effects of the rTMS depend on the location, intensity and frequency of stimulation. At the visual cortex, they manifest themselves in the form of short-lived light sensations called phosphenes [4]. Earlier investigations have demonstrated that these visual sensations originate from the terminal parts of the optic radiation close to its ending in V1 as well as from tracts leading back from V2 and V3 to V1, so that a major role of V1 can be assumed [5]. An overview study reviewing recent findings about the effects of rTMS on a neurobiological level found evidence for changes in the expression patterns of several target proteins after excitatory and inhibitory rTMS [6].
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