Einfluss von pulsierender transkranialer Wechselstromstimulation auf die Bearbeitung der Stroop Aufgabe
Influence of pulsating transcranial alternating current stimulation on the processing of the Stroop task
Doctoral thesis
Date of Examination:2024-11-05
Date of issue:2024-10-29
Advisor:Prof. Dr. Andrea Antal
Referee:Prof. Dr. Andrea Antal
Referee:PD Dr. Peter Dechent
Referee:Prof. Dr. Ralf Dressel
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Abstract
English
Cognitive control is an essential everyday skill that is associated with increased activity in the left dorsolateral prefrontal cortex (LDLPFC) and the dorsal anterior cingulate cortex (dACC). Although the relevance of the individual brain areas in the context of cognitive control has already been demonstrated, the influence of LDLPFC and dACC communication on cognitive control is still unclear. In the present study, this inter-cortical communication was investigated in 48 subjects using non-invasive pulsed transcranial alternating current stimulation (ptACS) during the Stroop task. The Stroop task involves naming the font color of a word while suppressing the meaning of the word. In order to solve this task effectively, cognitive control must be applied, the extent of activation of which should be influenced by the ptACS. The central questions were, on the one hand, whether communication between cortical areas is essential for cognitive control and, on the other hand, whether ptACS is a suitable method for influencing the communication processes of neighboring brain areas. To answer these questions, the subjects were divided into two cohorts of 24 people each and received either isolated LDLPFC, isolated dACC, phase-shifted LDLPFC-dACC or placebo stimulation over four sessions, with the order of stimulation being randomized. The only difference between the individual cohorts was the stimulation duration (either 1 ms or 10 ms) and the effect of the stimulation was measured by the response time and response accuracy of the subjects. Based on the data collected, however, it became apparent that the use of ptACS in the present experimental setup appears to be unsuitable for investigating cognitive control. Neither the isolated stimuli nor the phase-shifted stimuli for influencing inter-cortical communication were able to demonstrate without contradiction a change in response times when processing the Stroop task as an expression of altered cognitive control. Although the effects already described could be partially reproduced (altered response times), the overall results across both cohorts were too inconsistent, so that all results should be critically scrutinized. The reasons for this inconsistency are unclear. One possibility could be suboptimal test conditions, which led to too much inter-individual variability between the test subjects. Another cause could be the currently still unclear cellular effects of ptACS, which may not have had the desired effect of changing the response time. For these reasons, the effectiveness and the basic mechanisms of ptACS should first be investigated in more detail in further experiments before it can be used as a potential instrument for research or as part of a therapy.
Keywords: Stroop task