Mindfulness, Pain, Placebo Effect, Transcranial Direct Current Stimulation (tDCS)
Conditions
Brief summary
In this experiment,the investigators study the effects of interpersonally induced placebo effects and a mindful awareness induction on negative affect. Specifically, it will be examining the effects of interpersonally induced placebo effects (sham tDCS vs. control) and a mindful awareness induction (mindful state vs. control), as well as their interaction. Each group will undergo fMRI scanning and physiological recording will performing the Multimodal Negative Affect Task (MNAT).
Detailed description
This study aims to investigate the effects of interpersonally induced placebo effects and a mindful awareness induction on negative affect. The study will involve 120 participants recruited from the Dartmouth College community, aged between 18 and 55, with an equal distribution of 60 males and 60 females. Participants will be assigned to the role of patient and will undergo fMRI scanning and physiological recording while performing the Multimodal Negative Affect Task (MNAT). The study design follows a 2 x 2 factorial design, examining the effects of interpersonally induced placebo effects (sham tDCS vs. control) and a mindful awareness induction (mindful state vs. control), as well as their interaction. A follow-up transfer assessment (1 week follow-up, session 2) will be conducted to examine the effects of the mindful state on verum motor tDCS stimulation. The participants will be randomly assigned to either the Mindfulness group or the No-mindfulness group, with 60 participants in each group and two sessions for each participant. In session 1, participants in the Mindfulness group will undergo a Mindful State Induction procedure aimed at promoting safety, relaxation, and receptivity. This induction procedure consists of two stages. In the first stage, participants will receive education about the brain's connection to and regulation of the body, emphasizing the endogenous brain regulatory capacities. The second stage involves a hypnotic induction of a relaxed state of receptivity using the Stanford Hypnotic Induction Profile (HIP) test of hypnotizability. This stage includes reclining the participant, suggesting that they are always in control, and making somatic suggestions to deepen the receptive state. A guided body scan, derived from mindfulness meditation, will further deepen the induced receptive state. In contrast, participants in the No-mindfulness group will go through comparable stages but with different instructions. In the first stage, they will receive education about pain and affect as protective processes of the body. In the second stage, they will be seated in an upright, alert posture and receive suggestions to focus on the task and suppress attention to the body. During the transfer test, conducted in a second fMRI session one week later, we will assess transfer to verum, open-label motor-cortex tDCS in an off-on-off design (both groups), with no explicit mindful state induction. No MRI data will be acquired during tDCS to avoid MR artifacts. We will also assess spontaneous use of strategies, including self-regulation and spontaneous adoption of states of mindful acceptance, and test whether these differ across groups. The analysis will involve assessing self-report measures, fMRI signatures, and autonomic reactivity to cues and task stimuli, similar to Experiment 1. The analysis will also explore the mediating role of interpersonal response (IPIX scores) and participants' initial responses to placebo. The researchers plan to control for sex, age, and experimenter effects in all analyses and will test for potential biological sex differences, disaggregating the data if necessary. MRI data will not be acquired during tDCS to avoid artifacts, and the study is not designed to directly compare placebo tDCS with verum tDCS. However, it aims to investigate interpersonal and suggestion-related contributions to open-label treatment responses, providing a foundation for future studies on tDCS and its interactions with placebo effects.
Interventions
BEHAVIORALtDCS stimulation (sham)
Participants will receive sham tDCS stimulation in a 20 minute long task. Targets will be fitted with the tDCS stimulation electrode cap and instructed that they will receive 20 minutes of tDCS stimulation for the task. Sham tDCS will target the motor cortex at 2mA for 15 sec at the beginning of the session, and then the stimulator will turn off. The participant will then sit for the remaining time of the session with the electrode cap on their heads but turned off and not delivering stimulation. All participants will receive sham tDCS stimulation (n=120).
BEHAVIORALtDCS stimulation (real)
In their second session, participants will receive real tDCS stimulation in a 20 minute long task. Targets will be fitted with the tDCS stimulation electrode cap and instructed that they will receive 20 minutes of tDCS stimulation for the task. Real tDCS stimulation will target the motor cortex at 2mA for 20 minutes (full duration of task). All participants will receive real tDCS stimulation (n=120).
BEHAVIORALMindful state induction
Experimenters trained in high-competence and high-warmth will train Group 1 participants on mindful state induction (n=60). Participants will undergo two stages for this training: 1) pain education to increase beliefs in endogenous brain regulatory capacities; and 2) the Stanford Hypnotic Induction Profile (HIP) test of hypnotizability and hypnotic induction of a relaxed state receptive to suggestion. In Stage 1, participants will receive education that pain and affect are processes designed to protect the body from danger, which are transmitted rapidly and automatically to the brain. In Stage 2, participants are (a) seated in an upright, alert posture; and (b) receive suggestions that the ability to attend to and discriminate affective perceptions is achievable and that suppressing attention to the body and focusing on the task will allow them to perform optimally under pressure. Mindful state induction will only be explicitly instructed during session 1 for Group 1 participants.
BEHAVIORALNo minfulness induction
Participants in the No-mindfulness group will go through comparable stages but with different instructions. In the first stage, they will receive education about pain and affect as protective processes of the body. In the second stage, they will be seated in an upright, alert posture and receive suggestions to focus on the task and suppress attention to the body.
Sponsors
Trustees of Dartmouth College
Study design
Allocation
NON_RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 55 Years
Healthy volunteers
Yes
Inclusion criteria
* No self-reported current or history of depression, bipolar disorder, or other psychiatric diagnosis * No self-reported current seizure disorder (i.e., seizure within past 10 years), or history of stroke or other major neurological diagnosis that can cause cognitive impairment * No self-reported current chronic pain, or acute pain within three months of the study period * No current migraine disorder (i.e., 15 headache days or more in 1 month) * No use of central nervous system-effective medication or other medication for neurological/psychiatric treatment * No self-reported substance abuse within the last six months * No contraindication to MRI or tDCS (e.g., pregnancy, claustrophobia, pacemakers, ear/cochlear implants, shrapnel injuries, clips, or other ferromagnetic/electrical objects/devices, diagnosed brain abnormality such as tumor, or skin lesions on the scalp.) * No contraindications for induced pain (e.g., no heart disease, high blood pressure, heart surgery, heart problems of any kind, severe asthma, respiratory problems of any kind, fibromyalgia, Raynaud's Syndrome or Disease, chronic pain, diabetes) * Participants must be capable of performing experimental tasks (e.g., are able to read), are fluent or native speakers of English * Participants must be able to tolerate the maximum level of thermal pain stimuli (for thermal stimuli)
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Pain Ratings | 3-10 sec post-stimulus throughout testing sessions, with all sessions complete within 1 month | Participants report subjective pain experience after each trial on a well-validated Generalized Linear Magnitude scale (GLMS) with anchors of No pain and Most intense pain imaginable. Raw units are on a 0-180 scale. |
| Subjective fear ratings | 3-10 sec post-stimulus throughout testing sessions, with all sessions complete within 1 month | Participants report subjective fear experience after each trial on a well-validated Generalized Linear Magnitude scale (GLMS) with anchors of No fear and Most intense fear imaginable |
| Cognitive effort ratings | 3-10 sec post-stimulus throughout testing sessions, with all sessions complete within 1 month | Participants report cognitive effort experience after each trial on a well-validated Generalized Linear Magnitude scale (GLMS) with anchors of No effort and Most effort imaginable |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Electrodermal autonomic responses to painful heat, fear-related images and cognitive effort. | Peri-stimulus throughout testing sessions, with all sessions complete within 1 month | Skin conductance (EDA) is recorded continuously throughout test sessions and per-stimulus amplitude of canonical stimulus-locked EDA responses is reported in microsiemens (uS). Higher values indicate a higher EDA response. |
Countries
United States
Contacts
Primary ContactTor Wager, Ph.D.
Outcome results
None listed