• Procedural motor learning (decrease in reaction time in ms) after the respective intervention (dopamine, transcranial direct current stimulation), compared to placebo
  

Adaptive behavior requires procedural motor learning, i.e. the acquisition of motor skills. Procedural learning is particularly critical in the rehabilitation of chronic motor deficits after stroke. A potent modulator of motor function and learning is found in the endogenous dopaminergic system. The investigator's own work could demonstrate that formation of an elementary motor memory, which constitutes the first step in acquiring more complex motor skills, can be enhanced in both healthy subjects and chronic stroke patients by pre-medication with levodopa. The aim of the present proposal is to:

• expand these exciting findings to procedural motor learning;
• explore the interaction with age, brain lesions, add-on interventions such as transcranial direct current stimulation (tDCS); and
• illuminate the underlying mechanisms.

The effect of levodopa +/- tDCS on procedural motor learning and cortical excitability will be studied in healthy volunteers and stroke patients. Then the investigator plans to delineate the underlying mechanisms of this effect by exploring N-methyl-D-asparate (NMDA) receptor-dependency of levodopa-enhanced learning and changes in activation and connectivity (using functional magnetic resonance imaging) in the respective neural networks resulting from the interaction of learning and dopaminergic neuromodulation.