Akute Auswirkungen transkranieller Gleichstromstimulation auf Parameter kortikaler Erregbarkeit
Acute effects of transcranial direct current stimulation on cortical excitability parameters
by Cornelia-Carmen Sturhan
Date of Examination:2012-07-24
Date of issue:2012-07-16
Advisor:Prof. Dr. Michael Nitsche
Referee:Prof. Dr. Michael Hülsmann
Referee:Prof. Dr. Knut Brockmann
Persistent Address:
http://dx.doi.org/10.53846/goediss-1571
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Abstract
English
Background: Non-invasive brain stimulation with weak direct currents (transcranial direct current stimulation, tDCS) enables the alteration of cortical activity and excitability of the human brain. It has been demonstrated that the effects of short-lasting tDCS, which induces no after-effects, depend on the activity of voltage-gated sodium and calcium channels.The aim of this study was to find out more about the neurophysiological origin of the tDCS-generated excitability changes. Methods: Depending on the stimulation protocol, the experiments were carried out in 12-20 healthy volunteers. tDCS was repetitively applied for a duration of 4 seconds. Cortico-spinal and intracortical excitability alterations were explored by transcranial magnetic stimulation (TMS). Specifically, the excitability of the corticospinal core area was explored by determination of motor thresholds, the activity of larger neuronal populations by the recruitment curve, and intracortical effects by short latency intracortical inhibition, intracortical facilitation, and I-wave facilitation. Results: For the corticospinal measures, tDCS elicited no alterations of motor thresholds, but anodal tDCS increased trendwise the slope of the recruitment curve, while cathodal tDCS diminished it. Significant changes of intracortical excitability were only revealed during cathodal tDCS at an interstimulus interval of 15 ms, showing reduced intracortical facilitation. Conclusion: tDCS affects corticospinal excitability, as shown by its impact on the recruitment curves. The diminution of intracortical facilitation during cathodal stimulation is might be caused by an additional alteration of NMDA receptors. The missing effects of tDCS on I-wave-activity and other parameters of intracortical facilitation and inhibition, which are all based on GABAergic und glutamatergic mechanisms, confirms the concept that the primary effects of tDCS are changes in membrane polarization
Keywords: Weak direct current stimulation; tDCS; TMS; cortical excitabilty; motor thresholds; input output curve; i-waves; inhibition; facilitation
Other Languages
Hintergrund: Ein Verfahren, um kortikale
Erregbarkeit und Aktivität zu verändern besteht in der
transkraniellen Stimulation des Motorkortex mit schwachem
Gleichstrom (tDCS). Dabei erhöht anodale und reduziert kathodale
Stimulation mit tDCS über dem primärmotorischen Kortex dessen
Exzitabilität. Pharmakologisch wurde bereits die Abhängigkeit der
durch kurz andauernde Stromstimulation bedingten Effekte von der
Aktivität der Natrium- und Calciumkanäle identifiziert. Auf dieser
Grundlage wurden in dieser Arbeit die genaueren
neurophysiologischen Zusammenhänge mit der Frage nach dem Ursprung
der Erregbarkeitsänderungen während tDCS untersucht. Methoden:
Abhängig vom Untersuchungsprotokoll wurden die Versuche an 12- 20
Probanden durchgeführt. tDCS erfolgte wiederholt für eine Dauer von
4 Sekunden. Die Exzitabilitätsänderungen wurden mittels
transkranieller Magnestimulation (TMS) erfasst. In verschiedenen
Protokollen wurden die Exzitabilität des kortikospinalen
Kerngebietes durch die Bestimmung der motorischen Schwellen, die
Aktivität größerer Neuronenpopulationen durch die Bestimmung der
Rekrutierungskurve,
Schlagwörter: Transkranielle Gleichstromstimulation; tDCS; TMS; kortikale Erregbarkeit; Motorische Schwellen; Input-ouput-Kurve; I-waves; Inhibition; Fazilitierung