The purpose of this study is to determine whether levodopa, pergolid, rivastigmine, or modafinil are effective in boosting semantic language acquisition in healthy subjects.

Our prior work shows that d-amphetamine and the dopamine precursor levodopa markedly improve word learning success in healthy subjects. In this randomized, placebo-controlled, double-blind clinical trial, we probe whether a mixed d1/d2 dopamine agonist (pergolid) or cholinergic neuromodulation (rivastigmine) or a general centrally arousing substance (modafinil) will yield a learning enhancement comparable to using levodopa in healthy subjects.

Our results show that the dopamine agonist pergolide impaired learning in healthy subjects compared to placebo, whereas cholinergic neuromodulation had no effect.

Inclusion Criteria:

• Healthy subjects
• 20-35 years old
• Right handedness
• Left language dominance (as assessed by functional transcranial Doppler ultrasonography [fTCD])

Exclusion Criteria:

• Neurological/psychiatric/metabolic/cardiac disorders
• Asthma
• Known allergic reactions to one of the experimental drugs
• Other drugs affecting the central nervous system
• Leisure drug ingestion during the past 4 weeks (urine test)
• Smoking cessation during the past 2 weeks
• > 6 cups of coffee or energy drinks per day
• > 10 cigarettes per day
• > 50 grams of alcohol per day