Modulation of Cognitive Flexibility by Transcranial Direct Current Stimulation, Tyrosine Administration and Polymorphisms in the COMT Gene
Conditions
Brief summary
The current study would examine whether increases in endogenous dopaminergic activity via tyrosine and the (presumed) excitation of these by anodal tDCS of the dlPFC could causally be related to cognitive flexibility as measured by task switching and reversal learning. Additionally, the study will test whether the Val158Met-polymorphism in the catechol- O-methyltransferase (COMT) gene could also predict the effect of TYR supplementation, as this gene is involved in DA degradation in the prefrontal cortex.
Interventions
COMBINATION_PRODUCTtdcs (sham/anodal) + drug (placebo/tyrosine)
tDCS= A DC Stimulator Plus (neuroConn, Germany) with one 5 cm x 7 cm rubber electrode (anode) and a 10 cm x 10 cm (cathode; reference electrode), encased in saline soaked sponges will be used. The anode will be positioned over the left dlPFC, centered on F3 in the 10e20 electroencephalography (EEG) system, while the cathode on the contralateral supraorbital ridge (Fp2).Current will be delivered at 1.5mA for 20 min plus 30 s fade in/fade out periods.For sham stimulation, the current will be faded in over 30 s, at 1.5mA and then will be switched off. Drugs= 2.0 g of L-Tyrosine and 2.0 g of the placebo microcrystalline cellulose will be dissolved in 400ml of orange juice as per previously published protocols.
Sponsors
Sheffield Hallam University
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 30 Years
Healthy volunteers
Yes
Inclusion criteria
* • Either male or female * 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, 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 * Drug treatment which may lower seizure threshold (i.e. epilepsy) * Pregnancy * Sleep deprivation (less than 6 hours a day) * A history of migraine or headaches * A history of taking antidepressants * A history of taking tyrosine supplements
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Wisconsin Card Sorting Test (WCST) performance | Measured twice in each session (4 arms): at time 0 and 80 minutes into testing. | Measuring change in perseverative errors in the WCST |
| Probabilistic Reversal Learning (PRL) performance | Measured twice in each session (4 arms): at time 0 and 80 minutes into testing. | Measuring change in reversal errors in the WCST |
| Flanker Task performance | Measured twice in each session (4 arms): at time 0 and 80 minutes into testing. | Measuring change in conflict cost (defined as the difference in reaction time between congruent and incongruent responses) |
Countries
United Kingdom
Contacts
Primary ContactLuca Aquili, Ph.D.
Backup ContactAnn Macaskill, Ph.D.
Outcome results
None listed