Effects of 20 Hz transcranial alternating current stimulation on the frontal oscillations during reversal learning
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The decisions we make are based on the feedback we receive. When actions are rewarded, they will be repeated, but if actions are punished, they will be avoided. Sometimes the environment we are surrounded by is changed, forcing us to adapt our behaviour to the new situation. Adapting one’s behaviour requires flexibility of the brain and this flexibility can be tested with reversal learning paradigms, where reward/punishment actions are changed during the task. We used a probabilistic reversal learning task (80/20), where the rewards and punishments were switched twice during the task, while stimulating with 20 Hz transcranial alternating current stimulation (tACS) over the frontal cortex. Furthermore, resting state electroencephalography (EEG) was recorded immediately before and after the stimulation. We aimed to establish the role of 20 Hz tACS on reversal learning, moreover whether it affects the speed by which one can learn a new rule, or if the rule implementation is affected. We further aimed to investigate the effect of tACS at 20 Hz on the frontal oscillating power bands. Our results indicate that both inter-hemispheric in-phase and anti-phase 20 Hz tACS increase performance during reversal learning compared to a control condition. However, effects were larger and more consistent for the inter-hemispheric in-phase condition. The improved performance was driven by a better ability to apply the learned rule, rather than an increase in learning speed. No effects were found between the experimental conditions when comparing the pre-post levels of theta or beta activity, nor of the theta/beta ratio.
Faculteit der Sociale Wetenschappen