tDCS for Cognitive Improvement in Healthy Subjects

Overseen By Minhtrang Chu

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of California, Davis

Must not be taking: Psychotropic medications

Disqualifiers: Head trauma, Vision issues, Pregnancy, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Approved in 2 Jurisdictions This treatment is already approved in other countries

Compensation: Varies

Number of Visits: 20

Duration: 1 month

75 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial explores how transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, affects thinking and memory skills in healthy individuals. It aims to understand the roles of different brain regions, such as the frontal and occipital areas, in tasks involving language, attention, and memory. Participants are divided into groups: some receive actual brain stimulation, while others undergo a placebo (fake) treatment. Suitable candidates have no history of head trauma and do not take psychiatric medications. As an unphased trial, this study offers participants the chance to contribute to groundbreaking research on brain function and cognitive enhancement.

Do I need to stop my current medications for the trial?

The trial does not specify if you need to stop taking your current medications, but it excludes those with a history of treatment with psychotropic medication (drugs affecting mood, perception, or behavior).

What prior data suggests that transcranial direct current stimulation (tDCS) is safe for cognitive improvement studies?

Research has shown that transcranial direct current stimulation (tDCS) is generally safe and well-tolerated. Studies focusing on the dorsolateral prefrontal cortex (DLPFC) have found tDCS to be safe, with no serious side effects reported. This indicates it could be a promising method for treating various conditions without major safety concerns.

For stimulation of the occipital cortex, past research also supports its safety. The tDCS methods used in this trial mirror those in previous studies, which have not resulted in serious adverse effects. Some minor effects, like skin irritation, might occur but are not considered serious.

Overall, evidence suggests that tDCS, when used as described in similar studies, is safe for participants. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about transcranial direct current stimulation (tDCS) because it offers a non-invasive way to potentially boost cognitive function by using low-level electrical currents. Unlike traditional cognitive enhancers that rely on medication, tDCS directly targets brain areas like the dorsolateral prefrontal cortex and the occipital cortex to modulate neural activity. This approach could offer a safer alternative with fewer side effects compared to drugs, and it might provide quicker results. By exploring different stimulation sites, like the DLPFC and occipital cortex, researchers hope to better understand and maximize the cognitive benefits of tDCS.

What evidence suggests that transcranial direct current stimulation (tDCS) is effective for cognitive improvement?

Research has shown that transcranial direct current stimulation (tDCS) can improve thinking skills. In this trial, participants may receive stimulation targeting the dorsolateral prefrontal cortex (DLPFC), which previous studies have shown can significantly enhance cognitive abilities, especially with higher electrical currents. One study revealed that 68.6% of participants who received active tDCS reported better cognitive performance, compared to 31.4% in the group that received a sham treatment.

This trial also includes an arm where participants receive stimulation at the back of the brain, specifically the occipital cortex. Research suggests that tDCS in this area can boost overall thinking abilities, as seen in conditions like mild cognitive impairment and Alzheimer's disease. It may also aid in cognitive training for conditions like schizophrenia. Overall, tDCS shows promise in improving brain functions related to thinking and memory. ^{6 7 8 9 10}

Are You a Good Fit for This Trial?

This trial is for healthy individuals aged 18-50 who speak and understand English well enough to complete cognitive tasks. They must be able to consent to the study. People with head trauma, psychotropic medication use, poor vision without correction, or conditions that contraindicate tDCS/MRI (like pregnancy or metal in the body) cannot participate.

Inclusion Criteria

I understand the study and can agree to participate.

I understand the study and can agree to participate.

ability to sufficiently speak and understand English so as to be able to understand and complete cognitive tasks

Exclusion Criteria

I have never had a head injury.

I am not pregnant, have no metal in my body, no serious health issues, no claustrophobia, no metallic implants, no skin conditions at electrode sites, and no brain disorders.

Corrected vision 20/30 or better

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants receive transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex or occipital cortex, or sham stimulation

1 month

Multiple sessions, each lasting 20 minutes

Follow-up

Participants are monitored for cognitive performance using behavioral and electrophysiological measures

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Transcranial Direct Current Stimulation

Trial Overview The study tests how transcranial direct current stimulation (tDCS) affects higher-order cognition like language comprehension and memory in healthy people and those with schizophrenia. It compares effects of stimulating different brain regions using behavioral tasks and EEG monitoring.

How Is the Trial Designed?

Group I: Occipital Stimulation Experimental Treatment 1 Intervention

Intervention. 20 minutes of 2 mA direct current stimulation over the occipital cortex.

Group II: DLPFC Stimulation Experimental Treatment 1 Intervention

Intervention. 20 minutes of 2 mA direct current stimulation over the dorsolateral prefrontal cortex.

Group III: Sham Stimulation Placebo Group 1 Intervention

Placebo Comparator. 0.5-1 minutes of 2 mA direct current stimulation over the dorsolateral prefrontal cortex followed by 19-19.5 minutes of sham stimulation

Who Is Running the Clinical Trial?

University of California, Davis

Lead Sponsor

Trials

958

Recruited

4,816,000+

Published Research Related to This Trial

A systematic review of 64 studies involving 2262 participants found that transcranial direct current stimulation (tDCS) has a low dropout rate (6% for active and 7.2% for sham), indicating good acceptability among participants.

Despite the low dropout rates, many studies inadequately reported adverse events (AEs), highlighting a need for improved guidelines to standardize AE reporting in tDCS research.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A Systematic Review on the Acceptability and Tolerability of Transcranial Direct Current Stimulation Treatment in Neuropsychiatry Trials. Aparício, LVM., Guarienti, F., Razza, LB., et al.[2018]

Transcranial direct current stimulation (tDCS) has a small but significant effect on improving reaction times in cognitive tasks for healthy older adults, particularly when applied online during tasks related to learning and memory, as well as executive function.

In contrast, offline tDCS did not show any significant impact on reaction times, indicating that the timing and method of tDCS application are crucial for its efficacy in enhancing cognitive functions in the elderly.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Transcranial direct current stimulation decreased cognition-related reaction time in older adults: A systematic review and meta-analysis. Lee, JH., Lee, TL., Kang, N.[2021]

Anodal transcranial direct current stimulation (tDCS) significantly improved cognitive performance in healthy elderly individuals by increasing neural activity, as evidenced by enhanced P200 and P300 amplitudes during a working memory task.

Cathodal tDCS also showed potential benefits for Alzheimer's disease patients, increasing P200 amplitude and frontal theta activity, suggesting that tDCS can modulate neural function differently based on the individual's cognitive state.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Behavioural and electrophysiological modulations induced by transcranial direct current stimulation in healthy elderly and Alzheimer's disease patients: A pilot study. Cespón, J., Rodella, C., Miniussi, C., et al.[2020]

Transcranial direct current stimulation (tDCS) has shown potential to improve cognitive functions such as processing speed, working memory, and executive functions in patients with mood disorders and schizophrenia, based on a systematic review of 41 studies.

The effects of tDCS on cognitive functioning and memory in Alzheimer's disease and mild cognitive impairment are less clear, with evidence being inconclusive or weak, highlighting the need for standardized protocols in future research.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Transcranial Direct Current Stimulation and Cognition in Neuropsychiatric Disorders: Systematic Review of the Evidence and Future Directions. Ciullo, V., Spalletta, G., Caltagirone, C., et al.[2022]

In a study involving 40 healthy participants, five sessions of transcranial direct current stimulation (tDCS) significantly enhanced executive functions, as evidenced by improved performance on neuropsychological and behavioral tests.

The tDCS stimulation activated key brain regions associated with executive functions, leading to increased brain activity in the Dorsolateral Prefrontal Cortex and other areas, suggesting a potential mechanism for its effectiveness in cognitive enhancement.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Underpinning the neurological source of executive function following cross hemispheric tDCS stimulation. Abul Hasan, M., Shahid, H., Ahmed Qazi, S., et al.[2023]

Transcranial Direct Current Stimulation (tDCS) is generally considered safe, but there are concerns that it could lead to significant negative effects in healthy individuals.

The scientific community needs to be alerted about the potential risks of tDCS, emphasizing the importance of protecting healthy volunteers from possible harm.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Safety of transcranial direct current stimulation in healthy participants. Boccard-Binet, S., Sen, A.[2021]

High-Definition transcranial Direct Current Stimulation (HD-tDCS) at amplitudes up to 4 mA was well tolerated by 292 older adults, with no safety-related adverse events reported and mostly mild sensations experienced during sessions.

The study demonstrated effective blinding for both participants and researchers, indicating that the sham stimulation was convincing, which supports the use of higher amplitudes for potentially greater therapeutic effects in older adults.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Tolerability and blinding of high-definition transcranial direct current stimulation among older adults at intensities of up to 4 mA per electrode. El Jamal, C., Harrie, A., Rahman-Filipiak, A., et al.[2023]

Transcranial direct current stimulation (tDCS) is a safe and affordable neuromodulatory technique that shows potential for modulating cognitive functioning, particularly in longitudinal studies where repeated sessions are used.

While tDCS has demonstrated some cognitive benefits, the effects are less consistent compared to its impact on motor outcomes, and more research is needed to understand the mechanisms behind its efficacy and to identify which individuals respond best to the treatment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cognitive Effects of Transcranial Direct Current Stimulation in Healthy and Clinical Populations: An Overview. Berryhill, ME., Martin, D.[2019]

Transcranial direct current stimulation (tDCS) applied to the left prefrontal cortex significantly improved verbal working memory and naming abilities in healthy adults, with effects lasting for 2 weeks after stimulation.

tDCS targeting the right prefrontal cortex enhanced visuospatial working memory, indicating that different areas of the prefrontal cortex can be stimulated for specific cognitive improvements.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Improvement of the working memory and naming by transcranial direct current stimulation. Jeon, SY., Han, SJ.[2022]

Transcranial Direct Current Stimulation (tDCS) has been shown to be safe, with no reports of Serious Adverse Effects or irreversible injuries across over 33,200 sessions involving more than 1,000 subjects, including vulnerable populations.

Safety assessments indicate that the current densities used in conventional tDCS (≤4 milliamperes) are significantly lower than those that could potentially cause brain injury, suggesting that tDCS protocols are well within safe limits.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Safety of Transcranial Direct Current Stimulation: Evidence Based Update 2016. Bikson, M., Grossman, P., Thomas, C., et al.[2022]

Transcranial direct current stimulation (tDCS) is generally considered safe, with mild and transient adverse effects reported in clinical trials, but the frequency and relationship of these effects with clinical variables remain unclear due to selective reporting bias.

Out of 209 studies reviewed, 117 mentioned adverse effects, with common issues like itching and tingling reported more frequently in the active tDCS group, although these differences were not statistically significant.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A systematic review on reporting and assessment of adverse effects associated with transcranial direct current stimulation. Brunoni, AR., Amadera, J., Berbel, B., et al.[2022]

In a study involving 43 participants, transcranial direct current stimulation (tDCS) targeting the left inferior frontal gyrus did not produce consistent improvements in fluency and working memory tasks, suggesting that the effects of tDCS may be unreliable.

The research highlights the need for further investigation into optimal stimulation parameters and protocols, as current single-session applications may not effectively enhance cognitive performance.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Null Effects on Working Memory and Verbal Fluency Tasks When Applying Anodal tDCS to the Inferior Frontal Gyrus of Healthy Participants. Westwood, SJ., Romani, C.[2020]

Citations

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Efficacy of transcranial direct current stimulation on ... tDCS demonstrated substantial efficacy in enhancing overall cognition in patients with PD. The efficacy of tDCS was obvious in executive function, language, ...

2. sciencedirect.com sciencedirect.com/science/article/pii/S0165178124005936

Transcranial direct current stimulation (tDCS) enhances ... A higher proportion of patients in active tDCS (68.6%) reported cognitive improvement compared to sham tDCS (31.4%). We concluded that tDCS can enhance ...

3. nature.com nature.com/articles/s41398-024-02994-w

Effect of transcranial direct current stimulation with ... Our results suggest that tDCS targeting the PPC relative to the DLPFC during concurrent cognitive performance may improve working memory in schizophrenia.

4. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC9138792/

Transcranial Direct Current Stimulation Enhances Cognitive ... Another meta-analysis found that anodic stimulation of tDCS on DLPFC significantly improved cognitive ability, especially at high-current ...

5. alzres.biomedcentral.com alzres.biomedcentral.com/articles/10.1186/s13195-025-01677-y

A systematic review and meta-analysis of the impact of ... tDCS demonstrated efficacy in enhancing global cognition in older people with cognitive impairments, providing insight into optimal parameters for clinical ...

6. sciencedirect.com sciencedirect.com/science/article/pii/S2590109523000447

Feasibility and Safety of Sequential Transcranial ... This study provides preliminary evidence about the feasibility, safety, and challenges to combine PT and tDCS in very frail older adults.

7. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC11549028/

Effects of Transcranial Direct Current Stimulation Targeting ... In conclusion, the tDCS targeting DLPFC may be a potentially effective therapeutic target for alleviating somatic symptoms in patients with MDD.

8. jamanetwork.com jamanetwork.com/journals/jamanetworkopen/fullarticle/2830597

Prefrontal Transcranial Direct Current Stimulation in ... ... tDCS over the prefrontal cortex . . . was safe and well tolerated", as well as the conclusion that "To establish tCDS as a therapeutic ...

9. nature.com nature.com/articles/s41598-023-39161-y

Frontal two-electrode transcranial direct current stimulation ... The present study suggests that single-session tDCS delivered in two two-electrode montages might not affect cognitive control or response inhibition.

10. translational-medicine.biomedcentral.com translational-medicine.biomedcentral.com/articles/10.1186/s12967-023-03989-9

Transcranial direct current stimulation to the left ... This study aimed to investigate whether tDCS over the left DLPFC improves non-dominant hand dexterity performance and determine if its efficacy depends on the ...