Studying the Role of Brain Molecules for Decision Making

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.

Study Overview

• Status: Recruiting
• Conditions: Healthy; Decision Making
• Intervention / Treatment: Drug: Methylphenidate; Drug: Placebo gum; Drug: Reboxetine; Drug: Nicotine gum; Drug: Placebo pill

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.

• Study Type: Interventional
• Enrollment (Anticipated): 160
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Philippe Tobler, PhD; Phone Number: 41446343745; Email: phil.tobler@econ.uzh.ch
• Study Contact Backup: Name: Hui-Kuan Chung, PhD; Phone Number: 41446343740; Email: hui-kuan.chung@econ.uzh.ch

Study Locations

• Switzerland
  • Zurich, Switzerland, 8006
    • Recruiting
    • University of Zurich
    • Contact: Philippe Tobler, PhD; Phone Number: 41446343745; Email: phil.tobler@econ.uzh.ch
    • Contact: Hui-Kuan Chung, PhD; Phone Number: 41446343740; Email: hui-kuan.chung@econ.uzh.ch
    • Sub-Investigator: Alexander Jetter, PD Dr. med.
    • Sub-Investigator: Quednow Boris, PhD
    • Sub-Investigator: Nikita Sidorenko, MSc

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 33 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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

Exclusion Criteria:

• Serious past brain disease or injury
• Frequent headaches (of any sort, > 1/week) or migraine (irrespective of frequency)
• History of epileptic seizures
• Any neurological disorder
• Surgery to head or heart (MRI safety, potential metal pieces)
• Pacemaker, hearing aid or neurostimulator (MRI safety, metal pieces)
• Known cardiac or cardiovascular disease or anomaly
• Family history of sudden death due to cardiac arrhythmia
• High or low blood pressure, history of heart attack, infrequent heartbeat
• Respiratory problems (including difficulty with breathing through the nose)
• Glaucoma (present or past)
• Insufficiency of kidney or liver, acute liver disease
• Any psychiatric disorder (especially depression, mania, schizophrenia, addiction panic and suicidality)
• Severe vocal or motor tics (methylphenidate, data quality)
• Severe psychosomatic disorder (somatic complaints without clear medical cause, has a mental component)
• Potential metal parts in body (MRI safety; metal splinters, gun wounds, shrapnel or surgical clips)
• Pregnancy, nursing, or currently planned pregnancy
• Allergy to drugs, particularly methylphenidate, reboxetine or nicotine
• Severe intolerance to lactose including strong diarrhea after only a few mg (weak lactose intolerance is no exclusion criterion as medication only contains a very small dose (around 4 mg) of lactose)
• Oversensitivity to hot pepper sauce (e.g., tabasco)
• Currently taking any medication or recently participated in other clinical trials that might interfere with Methylphenidate and Reboxetine, especially MAO-Inhibitors (e.g. Aurorix (Moclobemid) and Azilect (Rasagilin), antipsychotics, antibiotics, and medication for heart diseases
• Currently taking any further medication (besides birth control) or natural products (infrequent intake of natural products and/or food supplements need to be mentioned to the examiner)
• Drug abuse (exclude people with a positive test)
• Serious acute or chronic disease that could interfere with participation in the experiments
• Inability to lie still in the scanner (e.g. due to itching, sneezing, coughing, claustrophobia)
• Inability to understand the instructions
• Participants with BMI < 18
• Clinically relevant score in STAI T (anxiety), measured during screening on a separate day
• ECG demonstrating QTcF >450 msec or a QRS interval >120 msec at screening. If QTcF exceeds 450 msec, or QRS exceeds 120 msec, the ECG should be repeated two more times and the average of the three QTcF/QRS values should be used to determine participant eligibility, measured during screening on a separate day
• Participants who eat or drink grapefruit or grapefruit related citrus fruits (e.g., Seville oranges, pomelos) or drinks from 7 days prior to the administration of study medication.
• Participants who eat or drink any food/beverage containing caffeine or alcohol 12 hours before the study
• Current smokers/tobacco consumers (exclude people whose cotinine level is higher than 50ng/ml with a urine test)
• Phenylketonuria
• Dental or jaw condition prohibiting gum chewing
• Pheochromocytoma
• Thyroid disorders
• Diabetes
• Type of angina where chest pain occurs at rest
• Unpredictable severe constricting chest pain
• Prickling or tingling of fingers and toes
• Buerger's Disease
• Throat irritation
• Peptic ulcers
• Esophagitis

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Dopamine reuptake inhibitor; Participants in the dopamine reuptake inhibitor group will be asked to take one pill containing 20 mg methylphenidate 1.5 hours before the experimental session. One hour later (30 minutes before testing begins), participants will be asked to chew a placebo gum.	Drug: Methylphenidate; A 20 mg methylphenidate (Ritalin®) is administered only once for the dopamine reuptake inhibitor group.; Other Names: Ritalin®; Drug: Placebo gum; A placebo gum is administered only once.
Experimental: Noradrenaline reuptake inhibitor; Participants in the noradrenaline reuptake inhibitor group will be asked to take one pill containing 4 mg reboxetine 1.5 hours before the experimental session. One hour later (30 minutes before testing begins), participants will be asked to chew a placebo gum.	Drug: Placebo gum; A placebo gum is administered only once.; Drug: Reboxetine; A 4 mg reboxetine (Edronax®) is administered only once for the noradrenaline reuptake inhibitor group.; Other Names: Edronax®
Experimental: Cholinergic receptor agonist; Participants in the cholinergic receptor agonist group will be asked to take a placebo pill 1.5 hours before the experimental session. One hour later (30 minutes before testing begins), participants will be asked to chew a gum with 2 mg of nicotine.	Drug: Nicotine gum; A 2 mg nicotine (Nicorette®) gum is administered only once for the cholinergic receptor agonist group.; Other Names: Nicorette®; Drug: Placebo pill; A placebo pill is administered only once.
Placebo Comparator: Placebo; Participants in the placebo group will be asked to take a placebo pill 1.5 hours before the experimental session. One hour later (30 minutes before testing begins), participants will be asked to chew a placebo gum.	Drug: Placebo gum; A placebo gum is administered only once.; Drug: Placebo pill; A placebo pill is administered only once.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Choice data	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.	All participants perform decision-making tasks after drug/placebo administration in the main experimental session lasting about 1 hour.
Response time data	Response times are measured from experimental tasks. The investigators calculate how long participants take to make decisions in each trial.	All participants perform decision-making tasks after drug/placebo administration in the main experimental session lasting about 1 hour.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The size of pupil dilation	Pupil size is measured using eye-tracker while participants perform the experimental tasks. Baseline pupil size is also measured before the drug/placebo administration.	Pupil size is measured in the main experimental session before drug/placebo administration and through study completion lasting about 1 hour.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Computational parameters estimated from experimental data	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.	All participants perform decision-making tasks after drug/placebo administration in the main experimental session lasting about 1 hour.

Collaborators and Investigators

• Sponsor: University of Zurich
• Investigators: Principal Investigator: Philippe Tobler, PhD, University of Zurich

Study record dates

Study Major Dates

• Study Start (Actual): December 17, 2020
• Primary Completion (Anticipated): May 31, 2023
• Study Completion (Anticipated): May 31, 2023

Study Registration Dates

• First Submitted: April 10, 2020
• First Submitted That Met QC Criteria: May 7, 2020
• First Posted (Actual): May 12, 2020

Study Record Updates

• Last Update Posted (Actual): May 18, 2022
• Last Update Submitted That Met QC Criteria: May 17, 2022
• Last Verified: May 1, 2022

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Adrenergic Agents; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Autonomic Agents; Peripheral Nervous System Agents; Cholinergic Agents; Psychotropic Drugs; Neurotransmitter Uptake Inhibitors; Membrane Transport Modulators; Antidepressive Agents; Dopamine Agents; Ganglionic Stimulants; Nicotinic Agonists; Cholinergic Agonists; Dopamine Uptake Inhibitors; Central Nervous System Stimulants; Adrenergic Uptake Inhibitors; Nicotine; Methylphenidate; Reboxetine
• Other Study ID Numbers: 2020-00044-BEH

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No