Transkranielle Gleichstromstimulation verbessert kognitive Leistung und moduliert funktionelle Hirnaktivität und Konnektivität

Zusammenfassung

Anodale transkranielle Gleichstromstimulation (anodal transcranial direct current stimulation, atDCS) kann kognitive Funktionen bei Menschen verbessern. Die neuronalen Grundlagen ihrer Funktionsweise wurden allerdings bisher noch unzureichend untersucht. In einer Plazebo-kon­trollierten Studie untersuchten wir daher die neuronalen Korrelate der Leistungsverbesserung in einer semantischen Wortfindungsaufgabe mittels funktioneller Magnetresonanztomografie (fMRT) bei gleichzeitiger Stimulation des linken Gyrus frontalis inferior (IFG), einem zentralen sprachrelevanten Gehirnareal. atDCS wurde dabei im MRT während der Aufgabendurchführung appliziert. Simultan gemessene aufgaben-spezifische sowie aufgaben-unabhängige Ruhe-fMRT (sog. resting-state) Messungen dienten zur Charakterisierung der Auswirkung von atDCS auf Hirnfunktionen. Der durch atDCS signifikant verbesserte Wortabruf ging mit einer selektiven Aktivitätsreduktion im linken ventralen IFG einher, welcher speziell für semantische Abrufprozesse eine Rolle spielt. Des Weiteren erhöhte atDCS die funktionelle Konnektivität des linken IFG und anderer sprachrelevanter Hirnareale im Rahmen der Ruhe-fMRT Untersuchung. Zusammenfassend konnte gezeigt werden, dass atDCS bedingte Leistungsverbesserungen mit charakteristischen Veränderungen von Hirnaktivität- und Konnektivität assoziiert sind, die u. U. erhöhte Verarbeitungseffizienz widerspiegeln.

Abstract

Excitatory anodal transcranial direct current stimulation (atDCS) can improve human cognitive functions, but neural underpinnings of its mode of action remain elusive. In a cross-over placebo (“sham”) controlled study we used functional magnetic resonance imaging (fMRI) to investigate neurofunctional correlates of improved language functions induced by atDCS over a core language area, the left inferior frontal gyrus (IFG). Intrascanner transcranial direct current stimulation-induced changes in overt semantic word generation assessed behavioural modulation; task-related and task-independent (resting state) fMRI characterised language network changes. Improved word retrieval during atDCS was paralleled by selectively reduced task-related activation in the left ventral IFG, an area specifically implicated in semantic retrieval processes. Under atDCS, resting state fMRI revealed increased connectivity of the left IFG and additional major hubs overlapping with the language network. In conclusion, atDCS modulates endogenous low-frequency oscillations in a distributed set of functionally connected brain areas, possibly inducing more efficient processing in critical task-relevant areas and improved behavioural performance.

Schlüsselwörter

transkranielle Gleichstromstimulation - funktionelle Magnetresonanztomografie - semantische Flüssigkeit - Ruhe-fMRT - Eigenvektor-Zentralität

Key words

transcranial direct current stimulation - functional magnetic ­resonance imaging - semantic fluency - resting state fMRI - eigenvector centrality ­mapping

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