L-Tyrosine administration modulates the effect of transcranial direct current stimulation on working memory in healthy humans

Publikation: Beitrag in FachzeitschriftForschungsartikelBeigetragenBegutachtung

Beitragende

  • Bryant J. Jongkees - , Leiden University (Autor:in)
  • Roberta Sellaro - , Leiden University (Autor:in)
  • Christian Beste - , Klinik und Poliklinik für Kinder- und Jugendpsychiatrie (Autor:in)
  • Michael A. Nitsche - , Georg-August-Universität Göttingen, Technische Universität (TU) Dortmund, Ruhr-Universität Bochum (Autor:in)
  • Simone Kühn - , Max Planck Institute for Human Development, Universität Hamburg (Autor:in)
  • Lorenza S. Colzato - , Leiden University, Ruhr-Universität Bochum, Universität Kassel (Autor:in)

Abstract

Background Transcranial direct current stimulation (tDCS) is an increasingly popular method of modulating cognitive functions in humans. However, some doubt its efficacy as findings are inconsistent or remain unreplicated. It is speculated dopamine (DA) might play an important role in this inconsistency, by determining the direction and strength of the cognitive-behavioral effects of tDCS. However, so far evidence for this hypothesis has been correlational in nature, precluding definitive conclusions. Objective The present proof-of-principle study aimed at investigating a potentially causal role for DA in the effect of tDCS on cognition in healthy humans. Methods In Experiment 1 we aimed to replicate previous findings showing administration of DA's precursor L-Tyrosine (Tyr), presumably by inducing a modest increase in DA level, can enhance working memory (WM) performance as assessed with a verbal N-back task. In Experiment 2 we investigated the effect of Tyr administration on bilateral tDCS over dorsolateral prefrontal cortex (DLPFC) and WM. Results Experiment 1 showed Tyr administration enhances performance in a verbal N-back task. Experiment 2 showed Tyr modulates the effect of bilateral tDCS over DLPFC on WM. Specifically, tDCS had opposite effects on performance depending on current direction through the brain and Tyr administration. Conclusions The present study provides two major findings. First, we replicate Tyr's beneficial effect on verbal WM. Second, our results indicate a causal role for DA in the effect of tDCS on cognition. For this reason, we encourage future studies to consider the modulating effect of DA, as a step towards more consistent and replicable results regarding the efficacy of tDCS.

Details

OriginalspracheEnglisch
Seiten (von - bis)103-114
Seitenumfang12
FachzeitschriftCortex
Jahrgang90
PublikationsstatusVeröffentlicht - 1 Mai 2017
Peer-Review-StatusJa

Externe IDs

PubMed 28384480
ORCID /0000-0002-2989-9561/work/160952472

Schlagworte

Schlagwörter

  • Dopamine, Transcranial direct current stimulation, Tyrosine, Working memory