Clinical trial NCT03462303: Modulation of Cognitive Flexibility by Tyrosine Depletion and Transcranial Direct Current Stimulation
Official title: Modulation of Cognitive Flexibility by Tyrosine Depletion and Transcranial Direct Current Stimulation
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Cognitive Flexibility
Lead sponsor: Sheffield Hallam University
Sponsor class: OTHER
First posted: 2018-03-12
Enrollment: 36
Sex: ALL
Minimum age (years): 18
Maximum age (years): 30
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: FACTORIAL
Primary purpose: BASIC_SCIENCE

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.


Eligibility criteria: Inclusion Criteria:

* 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

Exclusion Criteria:

* 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

Primary outcomes:
measure: Change in cognitive flexibility performance
timeFrame: 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.
measure: Change in cognitive flexibility performance
timeFrame: 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.
Secondary outcomes:
Other outcomes:
Locations:
city: Sheffield
country: United Kingdom
facility: Department of Psychology labs
state: South Yorkshire
Study officials:
References: