A recent study at our lab showed increased episodic memory consolidation and response readiness after treatment with methylphenidate in healthy volunteers. The investigators seek to replicate and extend these findings. Furthermore the pharmacological specificity of these effects will be studied. Since methylphenidate has an effect on two neurotransmitters, dopamine and noradrenaline, either could be responsible for the observed effects. In order to explore the dopaminergic contribution to this effect, the study proposed here includes not only methylphenidate but also levodopa/carbidopa, which only affects dopamine and not noradrenaline.

In this study, 20 healthy males and females between 18 and 45 years of age will participate. They will be recruited via advertisements at Maastricht University and in local newspapers.

Participants will be treated once with methylphenidate, once with levodopa/carbidopa and once with placebo. All medications will be administered orally with a capsule.

It is hypothesized that methylphenidate and levodopa/carbidopa will both enhance episodic memory consolidation and improve response readiness

Inclusion Criteria:

• Male or female
• 18 to 45 years of age
• Healthy (i.e. absence of all exclusion criteria), normal static binocular acuity (corrected or uncorrected),
• Body mass index between 18.5 and 30
• Willingness to sign an informed consent.

Exclusion Criteria:

• history of cardiac, hepatic, renal, pulmonary, neurological, gastrointestinal, haematological or psychiatric illness.
• history of depression, bipolar disorder, anxiety disorder, panic disorder, psychosis, or attention deficit hyperactivity disorder will be excluded from participation.
• first-degree relative with a psychiatric disorder or a history with a psychiatric disorder
• excessive drinking (>20 glasses of alcohol containing beverages a week
• pregnancy or lactation
• use of medication other than oral contraceptives
• use of recreational drugs from 2 weeks before until the end of the experiment
• any condition in which gastrointestinal motility might carry any risk
• any sensory or motor deficits which could reasonably be expected to affect test performance