Predictors of Probabilistic Selection Task Performance

Not Applicable

• Conditions: Learning; Lack of (Specific)
• Interventions: Behavioral: Effects of tDCS of dlPFC on Probabilistic Selection Task

• Registration Number: NCT04798105
• Lead Sponsor: Charles Darwin University

Brief Summary

The project aims to investigate whether tDCS has an effect on reward and punishment learning sensitivity. Further, whether tDCS will modulate extraversion and impulsivity personality traits, and eye-blink-rate's effect on learning. For instance, trait extroversion in past research is linked to the dopamine neurotransmitter system, where it is thought that extreme low and high levels are detrimental to cognitive performance. Since tDCS has been shown to increase dopamine levels, it is thought that people who are already high in dopamine may experience less benefit (or even impairment) on cognitive performance following tDCS.

Detailed Description

The aim of this study is to investigate the effect of a non-invasive, low intensity and risk, brain stimulation technique known as transcranial direct current stimulation (tDCS) on the way people learn in a computer administered cognitive task. This will be achieved by comparing participants' performance on this task after receiving placebo 'sham' tDCS in one experimental session, and real 'treatment' tDCS in another experimental session. Neither the researcher administering the session or the participant will be aware of which form of tDCS is being used. Previous research indicates that tDCS of the left dorsolateral prefrontal cortex brain region stimulates the release of a chemical neurotransmitter, dopamine, that is linked to reward and punishment processing, and implicated in conditions such as addiction and Parkinson's disease.

The computerized cognitive learning task presents participants with pairs of six different symbols and asks them to choose one of these. In the first half of the task, participants receive visual feedback (correct or incorrect; +$0.10 or -$0.10) and the symbols are preprogrammed to be rewarded or punished for. In the second part of the task, participants are tested on the same task but do not receive feedback.

Further, the effect of participants' personality characteristics (specifically extraversion and impulsivity), as well as eye-blink-rate, on cognitive learning performance will be investigated, as this is known to be influenced by tDCS. Past research suggests that people may respond differently to tDCS based on individual differences in these personality traits, that are linked at a brain circuits level. Participants will be assessed on extraversion and impulsivity personality traits using pen and paper, self-report questionnaires. Similarly, eye-blink-rate is linked to the aforementioned brain neurotransmitter, dopamine, and will be assessed by manually counting of blinks in a video recording of the participant focusing on a stationary point.

Study Timeline

• Study First Submitted: 2021-03-09
• Study First Submitted QC: 2021-03-11
• Study First Posted: 2021-03-15
• Study Start: 2021-04-12
• Status Verified: 2021-07
• Last Update Submitted: 2021-07-26
• Last Update Posted: 2021-07-28
• Primary Completion: 2021-10-22
• Study Completion: 2021-10-22

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 30

Inclusion Criteria

• Either male or female
• You are aged between 18 and 50 years
• You are in good health
• You agree to fast 3 hours prior to testing

Exclusion Criteria

• Suffer from cardiac, hepatic, renal, and/or neurological disorders
• Have damaged or diseased skin on your face and scalp, or a sensitive scalp
• Have a history of alcohol or drug addiction, or severe psychiatric illness
• Are receiving drug treatment which may lower seizure threshold (i.e. epilepsy)
• Are pregnant
• Are sleep deprived (less than 6 hours a day)
• Have metallic dental fillings, orthodontic appliances, a cardiac pacemaker, cochlear implant, and/or surgical clips
• Have a history of migraine or headaches

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
tDCS anodal	Effects of tDCS of dlPFC on Probabilistic Selection Task	Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (dlPFC) in anodal/excitatory mode.
tDCS sham	Effects of tDCS of dlPFC on Probabilistic Selection Task	Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (dlPFC) in sham mode.

Primary Outcome Measures

Name	Time	Method
Change in Probabilistic Selection Task (PST) performance from pre tDCS to post tDCS	PST is tested prior to tDCS administration at time 0 (baseline) and following tDCS (approximately 50 minutes into the experiment) for both tDCS sham and tDCS anodal	Accuracy (%) and reaction times on the above task

Trial Locations

Locations (1)

Charles Darwin University, College of Health & Human Sciences; 🇦🇺 Darwin, Northern Territory, Australia