Modulation of Cognitive Flexibility by Tyrosine Depletion and Transcranial Direct Current Stimulation
1 other identifier
interventional
36
1 country
1
Brief Summary
The dorsolateral prefrontal cortex (dlPFC) and dopamine (DA) have been implicated in the control of cognitive flexibility. However, while a great deal of what it is know regarding a causative relationship between cognitive flexibility and its neuronal underpinning comes from animal studies, human data have largely been correlational (i.e. imaging investigations). In a recent study, the current research group examined whether putative increases in dopamine levels through tyrosine administration and blockage of these by cathodal (i.e. inhibitory) transcranial direct current stimulation (tDCS) of the dlPFC could be causally related to cognitive flexibility as measured by task switching and reversal learning. The next step involves finding a way of lowering dopamine concentrations while anodal (i.e. excitatory) stimulation of the dlPFC is applied and cognitive flexibility measured. One experimental approach to reduce global DA synthesis and transmission is through acute phenylalanine and tyrosine depletion (APTD). This dietary intervention involves the administration of an amino-acid mixture lacking in tyrosine and phenylalanine, which can be used to selectively lower DA synthesis in humans.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P25-P50 for not_applicable
Started Feb 2018
Shorter than P25 for not_applicable
1 active site
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
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Study Timeline
Key milestones and dates
Study Start
First participant enrolled
February 12, 2018
CompletedFirst Submitted
Initial submission to the registry
February 20, 2018
CompletedFirst Posted
Study publicly available on registry
March 12, 2018
CompletedPrimary Completion
Last participant's last visit for primary outcome
June 30, 2018
CompletedStudy Completion
Last participant's last visit for all outcomes
June 30, 2018
CompletedSeptember 11, 2018
September 1, 2018
5 months
February 20, 2018
September 10, 2018
Conditions
Outcome Measures
Primary Outcomes (2)
Change in cognitive flexibility performance
Measured using Wisconsin Card Sorting Test
Measured over 5 hours four times.1st measurement taken at baseline (i.e. time 0). 2nd measurement taken 120 minutes after measurement 1. 3rd measurement taken 220 minutes after measurement 1. 4th measurement taken 270 minutes after measurement 1.
Change in cognitive flexibility performance
Measured using Probabilistic Reversal Learning
Measured over 5 hours. 1st measurement taken at baseline (i.e. time 0). 2nd measurement taken 120 minutes after measurement 1. 3rd measurement taken 220 minutes after measurement 1. 4th measurement taken 270 minutes after measurement 1.
Study Arms (4)
tDCS sham + balanced drink
PLACEBO COMPARATORtDCS sham + tyrosine depleted drink
EXPERIMENTALtDCS anodal + balanced drink
EXPERIMENTALtDCS anodal +tyrosine depleted drink
EXPERIMENTALInterventions
Transcranial direct current stimulation (sham) of the dlPFC in combination with a tyrosine and phenylalanine free product.
Transcranial direct current stimulation (anodal) of the dlPFC in combination with a tyrosine and phenylalanine free product.
Transcranial direct current stimulation (sham) of the dlPFC in combination with a drink containing both tyrosine and phenylalanine.
Transcranial direct current stimulation (anodal) of the dlPFC in combination with a drink containing both tyrosine and phenylalanine.
Eligibility Criteria
You may qualify if:
- Either male or female
- You are aged between 18 and 30 years
- You are in good health
- You agree to fast overnight prior to testing
You may not qualify if:
- Are suffering from cardiac, hepatic, renal, or neurological disorders
- Damaged or diseased skin on your face and scalp, or a sensitive scalp
- A history of alcohol or drug addiction, or severe psychiatric illness
- Are in drug treatment which may lower seizure threshold (i.e. epilepsy)
- You are pregnant
- Slept less than 6 hours prior to coming to the lab
- Suffer from phenylketonuria
- A history of or current experience of migraine or headaches
- A history of or current use of antidepressants
- A history of or current use of tyrosine supplements
- Consume more than five beverages containing caffeine per day
Contact the study team to confirm eligibility.
Sponsors & Collaborators
Study Sites (1)
Department of Psychology labs
Sheffield, South Yorkshire, S10 2BQ, United Kingdom
Study Design
- Study Type
- interventional
- Phase
- not applicable
- Allocation
- RANDOMIZED
- Masking
- DOUBLE
- Who Masked
- PARTICIPANT, OUTCOMES ASSESSOR
- Purpose
- BASIC SCIENCE
- Intervention Model
- FACTORIAL
- Sponsor Type
- OTHER
- Responsible Party
- SPONSOR
Study Record Dates
First Submitted
February 20, 2018
First Posted
March 12, 2018
Study Start
February 12, 2018
Primary Completion
June 30, 2018
Study Completion
June 30, 2018
Last Updated
September 11, 2018
Record last verified: 2018-09