NCT03462303

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

• Status: Completed
• Phase: N/A
• Study type: Interventional
• Enrollment: 36 (actual)
• Sponsor: Sheffield Hallam University · Academic / Other
• Sex: All
• Age: 18 Years – 30 Years
• Healthy volunteers: Accepted

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.

Conditions

• Cognitive Flexibility

Interventions

Type	Name	Description
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.
COMBINATION_PRODUCT	Anodal tDCS and tyrosine depleted drink	Transcranial direct current stimulation (anodal) of the dlPFC in combination with a tyrosine and phenylalanine free product.
COMBINATION_PRODUCT	Sham tDCS and balanced drink	Transcranial direct current stimulation (sham) of the dlPFC in combination with a drink containing both tyrosine and phenylalanine.
COMBINATION_PRODUCT	Anodal tDCS and balanced drink	Transcranial direct current stimulation (anodal) of the dlPFC in combination with a drink containing both tyrosine and phenylalanine.

Timeline

• Start date: 2018-02-12
• Primary completion: 2018-06-30
• Completion: 2018-06-30
• First posted: 2018-03-12
• Last updated: 2018-09-11

Locations

1 site across 1 country: United Kingdom