NCT06980090

Neural Mechanisms of Interpersonal Expectations on Negative Affect

• Status: Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 190 (estimated)
• Sponsor: Trustees of Dartmouth College · Academic / Other
• Sex: All
• Age: 18 Years – 55 Years
• Healthy volunteers: Accepted

Summary

The goal of this clinical trial is to learn whether non-invasive brain stimulation, called transcranial temporal interference stimulation (tTIS), can reduce negative affect, and how expectations shaped by care providers influence these effects. The main questions this study aims to answer are: (1)Does active tTIS reduce negative affect more effectively than sham (inactive) tTIS? (2)Do positive treatment expectations enhance the effects compared to negative expectations? Participants will: (1) Receive either active or sham tTIS. (2) Be provided with positive or negative messaging regarding treatment effectiveness. (3) Interact with care providers and complete assessments measuring negative affect and physiological responses.

Detailed description

The study employs a within-subject, crossover factorial design, consisting of two experiments. Experiment 1 In Experiment 1, 30 participants ('patients') will complete all combinations of two independent variables-stimulation type (active vs. sham tTIS) and placebo manipulation (positive vs. negative placebo messaging)-resulting in four sessions: * Session A: Positive Placebo + Active tTIS * Session B: Positive Placebo + Sham tTIS * Session C: Negative Placebo + Active tTIS * Session D: Negative Placebo + Sham tTIS Participants complete three multimodal negative affect tasks (MNAT) before and after each stimulation session. Active tTIS delivers two signals at 2000 Hz and 2080 Hz, generating an 80 Hz interference beat targeted at the anterior/mid-cingulate cortex (aMCC) at 2 mA for 20 minutes. Sham tTIS uses identical frequencies (2000 Hz and 2000 Hz) with no effective interference. Sessions are administered in a counterbalanced order based on a Balanced Latin Square to minimize order effects, with at least 48 hours between sessions. Participants thus serve as their own controls. Experiment 2 Experiment 2 includes 160 participants divided into two groups: 120 'patients' and 40 'doctors'. A within-subject crossover design is employed, focusing specifically on placebo manipulation effects. Patients complete two experimental sessions involving sham tTIS only: * Session E: On-Placebo + Sham tTIS (with social placebo intervention) * Session F: Off-Placebo + Sham tTIS (without placebo intervention) In both sessions, patients complete the same MNAT tasks before and after stimulation. Sham tTIS involves a brief 15-second stimulation followed by no current for the remainder of the session, preserving the illusion of active stimulation. 'Doctors' are trained to administer the sham stimulation and deliver the placebo manipulation. During placebo induction sessions, providers simulate a "personalization" procedure, adjusting sham parameters while covertly reducing pain stimulus intensity to enhance placebo effects. Providers also monitor patients' nonverbal behavior and reported affect, offering feedback to enhance engagement and perceived treatment quality. Participants undergo MRI scanning, physiological monitoring, and behavioral assessments during Experiment 2. Multimodal physiological data-including ECG, respiration, skin conductance, photoplethysmography (PPG), and trans-radial electrical bioimpedance velocimetry (TRVE)-are collected using the BIOPAC 160 system.

Conditions

• Negative Affectivity
• Non-invasive Brain Stimulation
• Placebo Effect
• Expectations

Interventions

Type	Name	Description
BEHAVIORAL	Session A: Positive Placebo + Active tTIS	Participants receive active tTIS, with two signals set at 2000 Hz and 2080 Hz, creating an 80 Hz interference beat targeting the anterior/mid-cingulate cortex (aMCC). Stimulation is delivered at 2 mA for 20 minutes. The stimulation is combined with a positive social placebo intervention delivered by the care provider. Participants complete three multimodal negative affect tasks (MNAT) before and after the stimulation.
BEHAVIORAL	Session B: Positive Placebo + Sham tTIS	Participants receive sham tTIS, using two identical 2000 Hz signals that produce no low-frequency interference. The device mimics active parameters (2 mA, 20 minutes) without delivering effective stimulation. The sham stimulation is paired with a positive social placebo intervention. Participants complete three MNAT tasks before and after the session.
BEHAVIORAL	Session C: Negative Placebo + Active tTIS	Participants receive active tTIS (2000 Hz and 2080 Hz signals, 2 mA, 20 minutes) combined with a negative social placebo intervention (neutral or skeptical messaging about treatment efficacy). Participants complete three MNAT tasks before and after the stimulation.
BEHAVIORAL	Session D: Negative Placebo + Sham tTIS	Participants receive sham tTIS (identical 2000 Hz signals, mimicking active stimulation) combined with a negative social placebo intervention. Participants complete three MNAT tasks before and after the session.
BEHAVIORAL	Session E: On-Placebo + Sham tTIS	Participants receive sham tTIS (brief 15-second stimulation followed by no current) paired with a positive social placebo intervention. Participants complete three MNAT tasks before and after the session.
BEHAVIORAL	Session F: Off-Placebo + Sham tTIS	Participants receive sham tTIS (brief 15-second stimulation, then no current) without any placebo intervention. Participants complete three MNAT tasks before and after the session.

Timeline

• Start date: 2025-09-01
• Primary completion: 2026-08-31
• Completion: 2027-03-03
• First posted: 2025-05-20
• Last updated: 2025-12-09

Locations

1 site across 1 country: United States