Low Intensity Transcranial Electrical Stimulation: Effects on Categorization and Methodological Aspects

Transkranielle Stromstimulation mit geringen Intensitäten: Die Effekte auf Kategorisierungsleistung und methodische Aspekte

by Géza Gergely Ambrus
Doctoral thesis
Date of Examination:2012-05-21
Date of issue:2012-08-02
Advisor:Prof. Dr. Andrea Antal
Referee:Prof. Dr. Andrea Antal
Referee:Prof. Dr. Uwe Mattler
Referee:Prof. Dr. Michael Waldmann
Persistent Address: http://hdl.handle.net/11858/00-1735-0000-000D-EF6F-7

 

 

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Abstract

English

Low intensity transcranial electrical stimulation (tES) not only offers the possibility of clinical intervention in neurological disorders and conditions, but also provides us with a powerful research tool for understanding the workings of the intact human brain. The first study presented in the thesis offers evidence that applying tES stimulation to the dorsolateral prefrontal cortex can influence categorization performance in the “A, not A“ version of the prototype distortion test; the results show a disappearance of the prototype effect when this area is stimulated using anodal transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS). The similarity between the effects of tRNS and anodal tDCS further supports tRNS as a promising method in research and clinical applications. To assess the procedural sensations and discomfort associated with tES we have quantified the cutaneous perception characteristics of both tDCS and tRNS for short duration stimulations at different intensities, and have found that the application of tRNS involves substantially less procedural discomfort. This finding suggests that when cutaneous perception is an issue (e.g. blinding) tRNS may be better suited for certain purposes. We have also tested the cutaneous perception characteristics of tDCS and tRNS using round and rectangular electrodes to test whether the application of round electrodes reduces the procedural sensations associated with the stimulation. We have found that the round electrode configuration did not have an advantage in that regard. The time-course of the procedural discomfort associated with tDCS and the Fade in – Short stimulation – Fade out (FiSsFo) sham stimulation method has been investigated in a third methodological study. We have found that investigators (participants of the study who were conducting experiments using tES methods themselves) could more easily distinguish between verum and sham stimulation than naïve and experienced subjects. Furthermore, we have found that the cutaneous perception does not disappear in the first phase of the stimulation as previously reported, but never quantitatively assessed. Nevertheless, when taking only naïve and experienced participants into account, no differences in the levels of perceived stimulation strength could be observed, thus the FiSsFo method may be considered a reliable approach to blinding in tDCS research.
Keywords: dorsolateral prefrontal cortex; prototype distortion task; transcranial direct current stimulation; transcranial random noise stimulation; placebo

Other Languages

Transkranielle Stromstimulation mit geringen Intensitäten (tES) bietet nicht nur die Möglichkeit der klinischen Intervention bei neurologischen Erkrankungen, sondern ist auch ein leistungsfähiges Forschungswerkzeug, um die Funktionsweise des gesunden menschlichen Gehirns besser verstehen zu können. Die erste Studie, die in der Arbeit dargestellt ist, zeigt, dass eine tES des dorsolateralen prefrontalen Kortex die Kategorisierungsleistung in der „A, not A“ Version des Prototypendistorsionstest beeinflussen kann. Diese Ergebnisse zeigen ein Verschwinden des Prototypeneffekts, wenn dieses Hirnareal mit anodaler transkranieller Gleichstromstimulation (tDCS) und transkranieller Zufallsrauschstimulation (tRNS) stimuliert wird. Die
Schlagwörter: dorsolateralen prefrontalen Kortex; Prototypendistorsionstest; transkranieller Gleichstromstimulation (tDCS); transkranieller Zufallsrauschstimulation (tRNS); Placebo
 
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