Brain Stimulation, Cognition, Healthy, Neurophysiology, Psychomotor Performance, Transcranial Direct Current Stimulation (tDCS)
Conditions
Keywords
Transcranial Electrical Stimulation, Non-Invasive Brain Stimulation, Neuromodulation, Sham-Controlled Study, Double-Blind Study, Cognitive Enhancement, Working Memory, Attention, Learning and Memory, Task Performance, Human Performance, Operational Performance, Neurocognitive Function, Brain-Behavior Relationships, Dorsolateral Prefrontal Cortex, Anterior Insula, Neuronal Excitability, Functional Near-Infrared Spectroscopy (fNIRS)
Brief summary
The objective of this randomized, double-blind, sham-controlled, crossover study is to evaluate the effects of transcranial electrical stimulation (tES) on complex cognitive task performance in healthy adult volunteers. The primary questions this study aims to answer are: 1. Does tES improve task performance, including speed, accuracy, and overall success, during a computerized track-and-capture task? 2. Do different stimulation targets produce differential effects on performance? 3. Are there short-term post-stimulation effects on task performance (up to 48 hours)? Participants will: 1. Complete two testing sessions under either active or sham stimulation conditions. 2. Perform a complex operational task involving dual-hand controllers while undergoing tES or sham stimulation, and immediately after. 3. Return for follow-up task performance assessments at 24 and 48 hours post-stimulation to evaluate after-effects.
Detailed description
Transcranial electrical stimulation (tES) is a non-invasive neuromodulation technique that delivers low-intensity electrical currents (e.g., \<2 mA) through scalp electrodes to modulate brain activity. Numerous studies have shown that tES can enhance cognitive functions such as learning, memory, attention, and decision-making in healthy individuals, as well as provide therapeutic benefits in psychiatric and neurological populations. Despite these findings, substantial knowledge gaps remain regarding the effects of tES, particularly in the context of complex, operationally relevant tasks. Existing research has primarily focused on the effects of tES on simple cognitive tasks, with limited investigation into task that require multiple cognitive domain to operate simultaneously. Performance on complex tasks, such as those involving motor coordination, visual-spatial process, decision-making, and rapid response, may respond differently to tES than simple, isolated tasks. Understanding these effects could have broad applications in optimizing cognitive performance across various high-demand settings. This study is designed to address several key uncertainties: 1. Inter-individual variability in behavioral and neurophysiological responses to tES. 2. the impact of stimulation parameters (location, type, intensity) on task performance. 3. The magnitude and duration of both immediate and post-stimulation effects on behavior. To investigate these questions, healthy adults perform a computerized track-and-capture task requiring real-time motor control and decision-making using dual-hand controllers. Participants undergo both active and sham stimulation in a randomized, double-blind, crossover design. Stimulation will target either the left dorsolateral prefrontal cortex or the left anterior insula, guided by current flow modeling software. Performance is assessed during stimulation, immediately after, and at 24 and 48 hours post-stimulation to evaluate both immediate and short-term after-effects. Outcome measures include task performance metrics (e.g., speed, accuracy, overall success) and neurophysiological data collected via non-invasive monitoring with functional near-infrared spectroscopy (fNIRS). The study is part of a broader research effort to characterize the functional impact of tES on complex behavior and to inform future applications in cognitive performance enhancement. All stimulation procedures follow established safety guidelines for low-intensity tES, including continuous monitoring of electrode impedance and post-session adverse event questionnaires assessing discomfort, mood, and cognitive status. The Soterix Medical MXN-33 HD-tES system includes built-in safeguards to prevent excessive current delivery and to ensure safe electrode contact throughout the stimulation. Participants serve as their own controls in a within-subject crossover design, increasing statistical power for detecting within-subject differences between active and sham conditions.
Interventions
Active tES delivered using the Soterix Medical MXN-33 HD-tES stimulator. Stimulation is applied via high definition electrodes targeting either the left DLPFC or L-aINS at intensities up to 1.9 mA. Stimulation is performed for up to 45 minutes during task execution. Participants perform the ROBoT-r task during stimulation.
Sham tES using the same Soterix Medical MXN-33 HD-tES stimulator and electrode placements. Stimulation ramps up and down over 20 seconds to mimic sensation but provides no continuous current. Participants perform the ROBoT-R task under sham conditions.
Sponsors
Study design
Masking description
Participants and investigators were blinded to stimulation conditions (active vs. sham) and to which pre-programmed stimulation protocol (A or B) corresponded to active stimulation. The investigator was aware of the assigned stimulation location (DLPFC or L-aINS), but not whether stimulation protocol A or B was active or sham. The tES device was operated in double-blind model, with stimulation order randomized.
Intervention model description
Participants are randomized to one of two stimulation location groups: (1) left dorsolateral prefrontal cortex (DLPFC) or (2) left anterior insula (L-aINS). Randomization is valances based on gender, age, and video gaming experience. Within each group, participants undergo a crossover design in which they receive both active and sham transcranial electrical stimulation (tES) in randomized order. This design allows for within-subject comparisons between stimulation conditions while assessing the impact of stimulation site on task performance.
Eligibility
Inclusion criteria
* Age 25 to 55 years * Master's or Doctorate degree, or equivalent relevant experience * No history of head injury or neurological or psychiatric disorders * No history of cardiac disease * No metal implants in the head * No implanted electronic devices * Not taking medication affecting neural or cardiovascular function * Able to provide written, dated informed consent
Exclusion criteria
* Smoking within the past year * Current illegal drug use * Alcohol abuse * Pregnancy (confirmed by urine test) * Participation in another brain stimulation protocol within the past month
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| ROBoT-r Task Performance Score (During Stimulation) | 5 minutes after stimulation onset | Performance on the ROBoT-r computerized track-and-capture task assessed using a weighted performance score that integrates accuracy, speed, and task success metrics. Scores are scaled from 0 to 100, with higher scores indicating better performance. Participants used dual-hand controllers to grapple a simulated spacecraft in a time-limited, physics-based environment. Performance was assessed during task execution concurrent with stimulation. |
| ROBoT-r Task Performance Score (Post-Stimulation) | 15 minutes post stimulation | Performance on the ROBoT-r task 15 minutes after completion of tES. Performance is quantified using a weighted composite score. Scores range from 0 to 100, with higher scores indicating better overall task performance. |
| ROBoT-r Task Performance Score (Post-Stimulation Follow-up) | 24 and 48 hours post-stimulation | Performance on ROBoT-r task at 24 and 48 hours after completion of tES. Performance is quantified using a weighted composite score. Scores range from 0 to 100, with higher scores indicating better overall task performance. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| tES Adverse Effects Questionnaire | Immediately following each stimulation session (active and sham), up to approximately 45 minutes per session. | Self-reported adverse effects were recorded immediately following the 45-minute stimulation. Participants reported common stimulation-related sensations (e.g., tingling, scalp pain, itching, burning, headache). Effects were recorded for both active and sham stimulation conditions. |
| fNIRS Data Availability | Throughout study sessions when fNIRS was collected (during stimulation and post-stimulation follow-ups). | Functional near-infrared spectroscopy (fNIRS) data were collected during task performance. This outcome reports the number of participants with usable fNIRS data available within each stimulation location group. Hemodynamic activation analyses are not reported here and may be provided in a future update. |
Countries
United States
Contacts
Massachusetts General Hospital
Participant flow
Recruitment details
Participants were recruited from the greater Boston area. Enrollment occurred between December 1, 2022 and October 10, 2024. All participants were screened for eligibility prior to enrollment
Pre-assignment details
A total of 44 participants provided informed consent and were enrolled. Four participants withdrew prior to assignment to a stimulation group due to scheduling conflicts and did not receive any study intervention. Therefore, 40 participants were assigned to study groups and are included in the participant flow.
Baseline characteristics
| Characteristic | — |
|---|---|
| Age, Continuous | 34.5 years STANDARD_DEVIATION 8.9 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 2 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 38 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants |
| Race (NIH/OMB) Asian | 13 Participants |
| Race (NIH/OMB) Black or African American | 0 Participants |
| Race (NIH/OMB) More than one race | 0 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Race (NIH/OMB) White | 27 Participants |
| Region of Enrollment United States | 40 participants |
| Sex: Female, Male Female | 22 Participants |
| Sex: Female, Male Male | 9 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk |
|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 19 | 0 / 20 | 0 / 20 | 0 / 20 |
| other Total, other adverse events | 12 / 19 | 11 / 20 | 14 / 20 | 13 / 20 |
| serious Total, serious adverse events | 0 / 19 | 0 / 20 | 0 / 20 | 0 / 20 |