Expectations, Motor Learning
Conditions
Keywords
tDCS
Brief summary
The purpose of this study is to test if priming expectations of transcranial Direct Current Stimulation (tDCS) can improve the efficacy of tDCS in enhancing motor learning.
Detailed description
Transcranial direct current stimulation (tDCS) is currently being investigated by the scientific community as an intervention to improve motor learning in the context of neurorehabilitation (e.g., recover lost motor function after stroke) and performance enhancement (e.g., improve sports or technical skill training). More importantly, consumers believe that tDCS works. The expectation surrounding the benefits of tDCS for skill enhancement is so pervasive that the technology is sold for less than $200 and highly rated by the general public on Amazon.com. At the same time, there is considerable skepticism within the motor control field regarding the efficacy and mechanism of action of tDCS on motor learning, driven by highly irreproducible and equivocal findings between and even within laboratories. How effective is tDCS, and could the positive effects of tDCS be attributable in part to a strong placebo effect? Placebo effects (i.e., a positive expectation associated with positive treatment outcomes), are well documented in other interventions like surgeries and pharmaceuticals, but have not been investigated in detail for tDCS, particularly in the motor domain. The lack of knowledge or consideration of the placebo effect may therefore explain why tDCS findings are so inconsistent within motor learning. Thus, the overall aim of this project is to determine whether people's expectations about tDCS change as a function of information about tDCS itself, and whether these changed expectations modulate the effects of tDCS on motor learning. Transcranial direct current stimulation (tDCS) is a noninvasive, safe cortical stimulation technique that has been effectively used for enhancing and inhibiting sensory and motor performance when applied to the responsible cortical areas in healthy adults. For instance, anodal tDCS of primary motor area can improve motor execution. Recent research has investigated whether it is the expectation of receiving tDCS that has a greater impact on behavioral outcomes compared to the actual application of tDCS. This is important as many domains of science are challenged to reproduce previous research demonstrating a positive effect of tDCS on behavior. Thus, to decipher legitimate effects of tDCS on behavior it is important to quantify and compare how changes in behavior are related to tDCS, a key metric related to strength of the placebo effect, and how malleable these placebo effects are. Individuals may participate in this study for up to four sessions (up to 3 training sessions and up to 1 follow-up visit, as assigned) in the span of approximately one week. The investigators expect that individuals will spend up to one hour during the training sessions, and (if applicable) around 15 minutes to complete the follow-up visit, if assigned. The follow-up visit would occur one week after the final training session. This is a double-blind study in which participants will be randomly assigned to specific intervention methods.
Interventions
DEVICETranscranial Direct Current Stimulation
Transcranial Direct Current Stimulation (tDCS) is a minimal risk, non-invasive, neuromodulatory technique that involves the emission of a weak electrical current, traditionally via the placement of two electrodes attached to the scalp of a participant. tDCS is widely used for research purposes, the US FDA considers trials of tDCS as non-significant-risk. There are several review articles supporting the safety of tDCS usage in controlled human trials. According to a published meta-analysis , the use of conventional tDCS protocols in human trials (≤40 min, ≤4 mA) has not produced any reports of a Serious Adverse Effect or irreversible injury across over 33,200 sessions.
Sponsors
Arizona State University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
DOUBLE (Subject, Caregiver)
Masking description
Participants and Research Assistants will be blinded to the groups/treatment conditions unless the participant is a "control". The investigator and/or research administration team will screen, enroll and assign participants to groups.
Intervention model description
Participants will be assigned to one of 4 groups: control, tDCS1, tDCS2, or tDCS3.
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Must be 18 or older. Right-hand dominant * Right-hand dominant
Exclusion criteria
* Mixed-handed or ambidextrous * Left-hand dominant * Seizure(s) * Head injury resulting in a loss of consciousness that has required further investigation (including neurosurgery) * Migraines * Current medical diagnosis of a phycological or neurological condition * Any metal in head (outside of mouth) such as shrapnel or surgical clips * Any implanted devices (e.g. cardiac pacemaker, brain stimulator) * Skin condition on scalp (e.g. psoriasis) * Head wound that has not completely healed * Adverse reactions to tDCS or any other brain stimulation technique (e.g. TMS, tRNS) * Pregnant * Currently taking prescription medications or are self-medicating (including recreational drug use), other than the contraceptive pill?
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Performance on Motor Task One Week After Final Training Session | One-Week Follow-Up visit (Day 10) | This will be calculated as the average of two trials of the motor task that are completed one week after the last training session. The motor task is a timed test that requires participants to spoon two beans (kidney, raw) at a time from a center proximal "start" cup to three distal "target" cups as fast as possible. In short, this task requires multijoint coordination and limb reversal, and performance for each trial is measured in seconds. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in Motor Performance Over the Course of Training | Day 1, 2, and 3 | This outcome measure will be measured as the slope of the line fitted to the motor task performance across all 30 training trials (this includes Day 1, 2 and 3), when trial is transformed to a logarithmic scale. This transformation is done to account for the fact that change in performance is non-linear. The motor task is a timed test that requires participants to spoon two beans (kidney, raw) at a time from a center proximal "start" cup to three distal "target" cups as fast as possible. In short, this task requires multijoint coordination and limb reversal, and performance for each trial is measured in seconds. |
| Change in tDCS Expectations From Day 1 to Day 10 | Day 1 and Follow-Up (Day 10) | This will be the change (Day 1 minus Day 10) in expectations of tDCS. The tDCS expectation scores are taken from a 1-item survey adapted from the Expectation Assessment Scale, where scores range from 0 (no expectation) to 8 (high expectations); a score of 4 is considered neutral. |
| Average Dwell Time | One-Week Follow-Up (Day 10) | This is the average amount of time spent in the home cup for each repetition, averaged across the two follow-up trials. |
| Average Peak Reach Velocity | One-Week Follow-Up (Day 10) | his is the average peak velocity for the outward portion of each repetition, averaged across the two follow-up trials. |
| Variability in Transcranial Direct Current Stimulation Expectations | Days 1, 2, 3, and 10 | This is the coefficient of variation (CV) for tDCS expectation scores. It is calculated by dividing the standard deviation of the participant's expectations across study days (Days 1, 2, 3, and 10) by the mean expectation of these 4 study days. The tDCS expectation scores are taken from a 1-item survey adapted from the Expectation Assessment Scale, where scores range from 0 (no expectation) to 8 (high expectations); a score of 4 is considered neutral. |
| Post-tDCS Symptom Questionnaire Score | Days 1, 2, and 3 | This is calculated using a 14-item self-rated questionnaire, with answers for each item ranging from 1 ("absent") to 10 ("severe"). A daily average score (ranging from 1 to 10) was calculated for each participant by averaging the 14 items. The reported values represent the mean of these daily averages per group. Higher values represent more severe symptoms (a worse outcome). |
| tDCS Expectation Scores | Days 1, 2, 3, and 10 | The tDCS expectation scores are taken from a 1-item survey adapted from the Expectation Assessment Scale, where scores range from 0 (no expectation) to 8 (high expectations); a score of 4 is considered neutral. This score was collected for each participant in the experimental group (tDCS1, tDCS2, tDCS3) across study days (Days 1, 2, 3, and 10). |
Countries
United States
Contacts
PRINCIPAL_INVESTIGATORSydney Schaefer, PhD
Arizona State University
Baseline characteristics
| Characteristic | — |
|---|---|
| Age, Continuous | 22.27 years STANDARD_DEVIATION 3.73 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 5 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 20 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants |
| Race (NIH/OMB) Asian | 24 Participants |
| Race (NIH/OMB) Black or African American | 5 Participants |
| Race (NIH/OMB) More than one race | 2 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 5 Participants |
| Race (NIH/OMB) White | 8 Participants |
| Region of Enrollment United States | 39 Participants |
| Sex: Female, Male Female | 13 Participants |
| Sex: Female, Male Male | 12 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 / 25 | 0 / 38 | 0 / 38 | 0 / 39 |
| other Total, other adverse events | 0 / 25 | 0 / 38 | 0 / 38 | 0 / 39 |
| serious Total, serious adverse events | 0 / 25 | 0 / 38 | 0 / 38 | 0 / 39 |
Outcome results
None listed