Modulation of Cognitive Flexibility by Tyrosine Depletion and Transcranial Direct Current Stimulation

Cognitive Flexibility Clinical Trial

Official title:

Modulation of Cognitive Flexibility by Tyrosine Depletion and Transcranial Direct Current Stimulation

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT03462303
• Other study ID #: SheffieldHallamAquili2018
• Status: Completed
• Phase: N/A
• Start date: February 12, 2018
• Est. completion date: June 30, 2018

Study information

• Verified date: September 2018
• Source: Sheffield Hallam University
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial 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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 36
• Est. completion date: June 30, 2018
• Est. primary completion date: June 30, 2018
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 18 Years to 30 Years

Eligibility

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

Related Conditions & MeSH terms

• Cognitive Flexibility

Intervention

Combination Product:
• Sham tDCS and tyrosine depleted drink
Transcranial direct current stimulation (sham) of the dlPFC in combination with a tyrosine and phenylalanine free product.
• Anodal tDCS and tyrosine depleted drink
Transcranial direct current stimulation (anodal) of the dlPFC in combination with a tyrosine and phenylalanine free product.
• Sham tDCS and balanced drink
Transcranial direct current stimulation (sham) of the dlPFC in combination with a drink containing both tyrosine and phenylalanine.
• Anodal tDCS and balanced drink
Transcranial direct current stimulation (anodal) of the dlPFC in combination with a drink containing both tyrosine and phenylalanine.

Locations

Country	Name	City	State
United Kingdom	Department of Psychology labs	Sheffield	South Yorkshire

Sponsors (1)

Lead Sponsor	Collaborator
Sheffield Hallam University

Country where clinical trial is conducted

United Kingdom, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	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.
Primary	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.