Decision Making, Healthy
Conditions
Brief summary
The aim of the present project is to elucidate the neuropharmacological mechanisms underlying value (choice preference) and attention (choice randomness) processing in humans. More specifically, the investigators test whether dopaminergic, noradrenergic and cholinergic interventions affect neural and behavioral processing of valuation and attention during decision-making. The investigators do this by up-regulating dopaminergic, noradrenergic or cholinergic neurotransmission pharmacologically through administration of methylphenidate, reboxetine, or nicotine. We test the hypothesis that methylphenidate, reboxetine, or nicotine reduce choice randomness and that this effect is underpinned by an effect on attention and/or value processing.
Detailed description
To simultaneously assess and dissociate choice preference and randomness in stable environments, the investigators plan to use two tasks: (1) a variant of the RISKGARP task, a well-established risky decision-making task and (2) a modified Becker-DeGroot-Marshak task that measures choice preference and the width of preference representations with the range of willingness to pay procedure (range-WTP). Note that wider representations should result in more choice randomness. The investigators will assess choice randomness also by repeating the same decision questions several times within each task and by relating the preferences measured by the RISKGARP task to those measured by the range-BDM task by using the same options in both tasks. To assess the impact of changing environments and learning on choice preference and randomness, participants will perform two established exploration/exploitation tasks. One (3) is a foraging task that has been combined with different pharmacological manipulations and the other (4) is a variant of the four-armed bandit task, which allows distinguishing value- or information-based exploration from random choice. Blood and saliva samples may be taken. Blood samples may be used to determine levels of the administrated substances and to assess genetic variation. Saliva samples may be used to determine cortisol and testosterone levels.
Interventions
DRUGMethylphenidate
A 20 mg methylphenidate (Ritalin®) is administered only once for the dopamine reuptake inhibitor group.
DRUGReboxetine
A 4 mg reboxetine (Edronax®) is administered only once for the noradrenaline reuptake inhibitor group.
DRUGNicotine gum
A 2 mg nicotine (Nicorette®) gum is administered only once for the cholinergic receptor agonist group.
DRUGPlacebo pill
A placebo pill is administered only once.
DRUGPlacebo gum
A placebo gum is administered only once.
Sponsors
University of Zurich
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Masking description
All participants will receive the same instructions, and neither they nor the experimenters are informed which drug is used. Participants must take the drug in front of the investigator, to ensure correct intake and compliance.
Intervention model description
This is a double-blind, randomized, placebo-controlled, between-participant study. In this experiment. Participants will receive a preferential dopamine reuptake inhibitor, a selective noradrenaline reuptake inhibitor, a natural nicotinic acetylcholine receptor agonist, or placebo under double-blind conditions.
Eligibility
Sex/Gender
ALL
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* Physically and psychiatrically healthy (as defined by
Exclusion criteria
) men and women aged 18-35 years * Ability and willingness to participate in the study * Willingness to not eat or drink any food/beverage containing caffeine or alcohol 12 hours prior to the administration of study medication (asked in screening session) * Willingness to not eat or drink grapefruit or grapefruit related citrus fruits (e.g., Seville oranges, pomelos) from 7 days prior to the administration of study medication (asked in screening session) * Good command of English language (be able to understand the task instructions and in the unlikely case of adverse effects inform the examiner) * Signed informed consent
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Choice data | All participants perform decision-making tasks after drug/placebo administration in the main experimental session lasting about 1 hour. | Choice data made by participants are measured from the experimental tasks. More specifically, the investigators calculate choice preferences, such as the percentage of trials in which participants chose options with probabilistic outcomes in the RISKGARP task and the bids they made in the Range-WTP task, the percentage of exploitative/explorative choices in the four-armed bandit task, and the leaving time in the foraging task. Moreover, the investigators determine choice sub-optimality, such as the number of choices violating transitivity in the RISKGARP task, the inconsistency of bids in repeated trials in the Range-WTP task, the percentage of selecting the worst option in the four-armed bandit task, and the difference between optimal leaving time and actual leaving time in the foraging task. |
| Response time data | All participants perform decision-making tasks after drug/placebo administration in the main experimental session lasting about 1 hour. | Response times are measured from experimental tasks. The investigators calculate how long participants take to make decisions in each trial. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| The size of pupil dilation | Pupil size is measured in the main experimental session before drug/placebo administration and through study completion lasting about 1 hour. | Pupil size is measured using eye-tracker while participants perform the experimental tasks. Baseline pupil size is also measured before the drug/placebo administration. |
Other
| Measure | Time frame | Description |
|---|---|---|
| Computational parameters estimated from experimental data | All participants perform decision-making tasks after drug/placebo administration in the main experimental session lasting about 1 hour. | Computational parameters are estimated from the data of participants during the decision-making tasks. Specifically, mathematical models will be applied to above-mentioned choice data and/or response time data. The estimated parameters reflect choice preference and stochasticity and are complementary to the descriptive measurements mentioned above. For example, utility functions will be estimated and the choice preferences are described by the concavititvity of utility functions. |
Countries
Switzerland
Outcome results
None listed