The role of dopamine in perception

Preliminary evidence suggest that the neurotransmitter dopamine and in
particular dopaminergic innervation of the basal ganglia might play a role in
conscious perception. In the proposed study we aim to provide causal evidence
for this hypothesis.

The primary objective is to investigate the effects of dopamine receptor
stimulation on neural and behavioural measures of perception and consciousness.
The secondary objective is to establish the relation between the effects of
dopamine stimulation and baseline characteristics of individual subjects.

This study will use a within-subject, double-blind, placebo-controlled
randomized crossover design.

Subjects will receive 1.5 mg cabergoline or placebo on two different test
sessions in a randomized order.

After an initial intake session, the subject will have to visit the laboratory
site two times. At each visit they will have to complete a series of tasks
after receiving 1.5 mg cabergoline or placebo. Neural activity will be measured
with EEG or fMRI which are both safe methods with no long-term side effects. On
the day before each visit they will have to adhere to some simple restrictions
regarding medication, alcohol and drug intake. In the morning of each visit
they will have to refrain from smoking and stimulant-containing drinks. The
most common side effects of cabergoline in healthy volunteers include nausea,
dizziness, headache, sleepiness and a loss of concentration. Previous studies
have shown that the single dose of 1.5 mg cabergoline is well tolerated in
healthy adults. Considering the extensive exclusion criteria, screening
procedure and constant monitoring of the subjects, we do not expect serious
side effects.