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Transcranial direct current stimulation over the left prefrontal cortex increases randomness of choice in instrumental learning

Transcranial direct current stimulation over the left prefrontal cortex increases randomness of choice in instrumental learning

Authors: 
Zsolt Turia, Matthias Mittnerb, Alexander Opitza, Miriam Popkesa, Walter Paulusa, Andrea Antala
Year: 
2014
Journal: 
Cortex
Abstract: 


Introduction

There is growing evidence from neuro-computational studies that instrumental learning involves the dynamic interaction of a computationally rigid, low-level striatal and a more flexible, high-level prefrontal component.
Methods

To evaluate the role of the prefrontal cortex in instrumental learning, we applied anodal transcranial direct current stimulation (tDCS) optimized for the left dorsolateral prefrontal cortex, by using realistic MR-derived finite element model-based electric field simulations. In a study with a double-blind, sham-controlled, repeated-measures design, sixteen male participants performed a probabilistic learning task while receiving anodal and sham tDCS in a counterbalanced order.

Results

Compared to sham tDCS, anodal tDCS significantly increased the amount of maladaptive shifting behavior after optimal outcomes during learning when reward probabilities were highly dissociable. Derived parameters of the Q-learning computational model further revealed a significantly increased model parameter that was sensitive to random action selection in the anodal compared to the sham tDCS session, whereas the learning rate parameter was not influenced significantly by tDCS.

Conclusion

These results congruently indicate that prefrontal tDCS during instrumental learning increased randomness of choice, possibly reflecting the influence of the cognitive prefrontal component.

Keywords

transcranial direct current stimulation; dorsolateral prefrontal cortex; probabilistic learning task; exploration; exploitation; working memory

Corresponding author. Department Clinical Neurophysiology, University Medical Center, Georg-August University, Göttingen, Germany, Göttingen D-37075, Robert-Koch-Str. 40. Tel.: +49 551 39 1912310.

These authors contributed equally.

Copyright © 2014 Published by Elsevier Ltd.

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