In the first condition, volunteers will receive a dopamine (DA) precursor (L-dopa, 100mg). L-dopa will be combined with a dose of an Aromatic amino acid decarboxylase inhibitor (Benserazide) 25mg to multiplicate its bioavailability and with a dose of domperidone 10mg (peripheral antagonist of DA) to minimize the risk of side effects.

In the second condition, volunteers will receive a D2 antagonist (Sulpiride, 800mg)

In the third condition, volunteers will receive a placebo (lactose)

In the first condition, volunteers will receive a 100mg dose of L-dopa, 25mg dose of Aromatic amino acid decarboxylase inhibitors (Benserazide) and 10mg dose of Domperidone. In the second condition, volunteers will receive Sulpiride 800mg. In the third condition, volunteers will receive placebo Reality-monitoring performances will be evaluated with a standardized task. Working-memory will be evaluated with the n-back task. Self-monitoring performances will be observed during a speech production experiment in which speakers monitor their auditory feedback while speaking.

Speech Bayesian reasoning: This task is a home-made task investigating the influence of prior on speech processing. Subjects will be required to identify speech in ambiguous auditory stimuli. Visual Bayesian reasoning: This task investigates the influence of prior on visual processing. Subjects will be required to recognize morph between faces and house.

Measured with a behavioral task developed, validated and used in investigators lab.

During the memory retrieval phase, 48 words will be presented, including the 32 words presented during encoding as well as 16 new words. Subjects will be required to identify whether each word was previously heard, imagined or new. Three words lists will be used and assigned randomly depending on the substance condition (L-dopa, Sulpiride, placebo). Each verbal list will include 16 items with the "imagine hear" encoding condition and 16 items with the "listen" encoding condition.

A single measure including two variables of interest will account for the main evaluation criteria:

• The average conditional source-identification measure (ACSIM) which represents the overall ability to correctly retrieve the source, conditional on that item was recognized as already presented.
• The source misattributions,the number of confusions between heard and imagined events.

Regarding reality-monitoring, a single test in which investigators will also measure the reaction times at the reality-monitoring task and scores of subjective confidence rating for reality-monitoring responses. The variable of interest will be the number of high-confident incorrect source-recognition responses. Investigators finally measure the vividness of each "imagined" or "listened" word with Visual Analogue Scales (VAS) from 0 to 100.