Contribution of L-Tyrosine to Human Decision Making in Stressful Situations

Study Overview
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Brief Summary
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L-tyrosine is a chemical precursor of dopamine. Under specific conditions, tyrosine administration can increase brain dopamine levels and therefore several studies have explored whether tyrosine supplementation can have a beneficial effect on cognitive and behavioural performance that is dependent on dopaminergic function. However, the effects of tyrosine supplementation are mixed: some studies show positive effects while others do not. Stress leads to an increase in dopaminergic activity and turnover in the brain, resulting in a decrease in brain dopamine levels. We propose to study the contribution of tyrosine to decision making and more particularly to the processes of response selection (mediated by the prefrontal cortex and under the influence of the dopaminergic system) in stressful situations.

Official Title
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Contribution of L-Tyrosine to Human Decision Making in Stressful Situations

Conditions
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Stress, Psychological

Intervention / Treatment
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* Biological: Blood collection
* Drug: L-Tyrosine 500 Mg
* Drug: Placebo
* Behavioral: Cognitive tasks
* Other: Stress exposure
* Behavioral: Anxiety scale
* Device: Electromyography (EMG)
* Device: Electroencephalography (EEG)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: From 18 to 65 years of age Exclusion Criteria: Tyrosine intake within the previous 15 days History of neurological or psychiatric disorder History of nephrological or endocrine disorder or liver failure Hereditary tyrosinemia

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: The study is composed of 4 arms: Tyrosine treatment without stress exposure Tyrosine treatment with stress exposure Placebo treatment without stress exposure Placebo treatment with stress exposure Every participants will participate in the 4 arms in a random order.
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Tyrosine - Test<br>4 similar visits (day 0, day 3, day 6, day 9): Administration of L-tyrosine No stress exposure | Biological: Blood collection<br>* A blood sample will be collected before and after treatment administration<br>Drug: L-Tyrosine 500 Mg<br>* The participants will be administered 4 capsules of L-Tyrosine 500 mg per oral route<br>Behavioral: Cognitive tasks<br>* The participants will perform cognitive decision-making tasks: Simon task and masking task after treatment administration<br>Behavioral: Anxiety scale<br>* Spielberger's State Trait Anxiety Inventory (STAI) will be filled by the participants before and after cognitive tasks<br>Device: Electromyography (EMG)<br>* Electromyography measurements will be performed during cognitive tasks.<br>Device: Electroencephalography (EEG)<br>* Electroencephalography measurements will be performed during cognitive tasks.<br>|
| Experimental: Tyrosine - Stress<br>4 similar visits (day 0, day 3, day 6, day 9): Administration of L-tyrosine Stress exposure | Biological: Blood collection<br>* A blood sample will be collected before and after treatment administration<br>Drug: L-Tyrosine 500 Mg<br>* The participants will be administered 4 capsules of L-Tyrosine 500 mg per oral route<br>Behavioral: Cognitive tasks<br>* The participants will perform cognitive decision-making tasks: Simon task and masking task after treatment administration<br>Other: Stress exposure<br>* Unpleasant but not painful skin stimulations will be administered to the participants at variable intervals on the left leg during the cognitive tasks<br>Behavioral: Anxiety scale<br>* Spielberger's State Trait Anxiety Inventory (STAI) will be filled by the participants before and after cognitive tasks<br>Device: Electromyography (EMG)<br>* Electromyography measurements will be performed during cognitive tasks.<br>Device: Electroencephalography (EEG)<br>* Electroencephalography measurements will be performed during cognitive tasks.<br>|
| Experimental: Placebo - Test<br>4 similar visits (day 0, day 3, day 6, day 9): Administration of Placebo No stress exposure | Biological: Blood collection<br>* A blood sample will be collected before and after treatment administration<br>Drug: Placebo<br>* The participants will be administered 4 capsules of Lactose 500 mg (placebo) per oral route<br>Behavioral: Cognitive tasks<br>* The participants will perform cognitive decision-making tasks: Simon task and masking task after treatment administration<br>Behavioral: Anxiety scale<br>* Spielberger's State Trait Anxiety Inventory (STAI) will be filled by the participants before and after cognitive tasks<br>Device: Electromyography (EMG)<br>* Electromyography measurements will be performed during cognitive tasks.<br>Device: Electroencephalography (EEG)<br>* Electroencephalography measurements will be performed during cognitive tasks.<br>|
| Experimental: Placebo - Stress<br>4 similar visits (day 0, day 3, day 6, day 9): Administration of Placebo Stress exposure | Biological: Blood collection<br>* A blood sample will be collected before and after treatment administration<br>Drug: Placebo<br>* The participants will be administered 4 capsules of Lactose 500 mg (placebo) per oral route<br>Behavioral: Cognitive tasks<br>* The participants will perform cognitive decision-making tasks: Simon task and masking task after treatment administration<br>Other: Stress exposure<br>* Unpleasant but not painful skin stimulations will be administered to the participants at variable intervals on the left leg during the cognitive tasks<br>Behavioral: Anxiety scale<br>* Spielberger's State Trait Anxiety Inventory (STAI) will be filled by the participants before and after cognitive tasks<br>Device: Electromyography (EMG)<br>* Electromyography measurements will be performed during cognitive tasks.<br>Device: Electroencephalography (EEG)<br>* Electroencephalography measurements will be performed during cognitive tasks.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Reaction Time | Reaction Time at the cognitive tasks | At day 9 (9 days after enrollment) | 
| Number of incorrect responses | Number of incorrect responses at the cognitive tasks | At day 9 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Error negativity | Error negativity on motor evoked potentials (measured by EMG) | At day 9 | 
| Correlation coefficient between anxiety level and tyrosinemia | Correlation coefficient between anxiety level (measured by anxiety scale) and tyrosinemia (measured in blood sample) | At day 9 | 
| Correlation coefficient between anxiety level and plasma tyrosine | Correlation coefficient between anxiety level (measured by anxiety scale) and plasma tyrosine (measured in blood sample) | At day 9 | 
| Correlation coefficient between cortisolaemia and melatoninaemia | Correlation coefficient between cortisolaemia and melatoninaemia (measured in blood sample) | At day 9 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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L-tyrosine