Resting-state Connectivity and Individual Differences in Affective Placebo Responsiveness

March 18, 2026 updated by: Stefanie Brassen

Expectation effects on affective states are central to mechanisms relevant for mood disorders and their treatment. This study will test whether inter-individual differences in resting-state functional connectivity (rsFC) within emotion regulation networks is associated with affective placebo responsiveness in healthy volunteers. Approximately 50 healthy participants will be pooled from two cross-over placebo studies in which participants receive intranasal saline either labeled as "oxytocin" in the placebo condition or as saline in the control condition.

Primary indices of placebo responsiveness are placebo-control difference scores of mood state, emotional paradigm responses, as well as expectation and experience ratings.

rsFC will be estimated using the CONN toolbox. Confirmatory analyses will use an a priori seed-based approach, with prefrontal seeds derived from previous task-based fMRI findings on affective placebo effects. These analyses will be complemented by secondary summaries of within- and between-network connectivity across the saliency network, the fronto-parietal control network, and the default mode network.

We hypothesize that interindividual differences in target rsFC networks will be associated with affective placebo effects, indicating general, trait-like mechanisms of placebo responsiveness.

Study Overview

Status

Enrolling by invitation

Conditions

Intervention / Treatment

Detailed Description

Background Understanding the neurobiological mechanisms underlying expectation effects in the affective domain can provide important insights into therapeutic principles relevant to mood disorders.

Placebo and expectancy effects are substantial in mood-related interventions and can be elicited experimentally in healthy samples using standardized, instruction-based expectation inductions combined with sham treatment. In related experimental paradigms based on the same broader framework, experimentally induced positive expectations have been shown to enhance subjective mood and bias emotional information processing toward positivity even in the absence of an active pharmacological agent.

Recent work further emphasizes marked interindividual variability in these effects, suggesting that affective placebo effects are stronger when more cognitive resources are available and are accompanied by lateral prefrontal engagement together with stronger coupling in prefrontal-limbic networks.

This pattern motivates an individual-differences approach in which expectancy effects depend, at least in part, on the capacity to initiate and maintain instructed treatment beliefs and to translate them into downstream affective processing. Resting-state fMRI (rsfMRI) offers a well-established way to quantify intrinsic functional coupling among large-scale brain systems. Resting-state functional connectivity (rsFC) is commonly used to characterize individual-specific and partly trait-like components of functional network organization, while also encompassing state-dependent variance and measurement constraints.

Such individual differences in rsFC have been linked to variability in executive functioning and broader phenotypic differences across healthy and clinical populations.

In the context of placebo mechanisms, rsFC involving frontoparietal control circuitry has been associated with individual differences in cue- and expectancy-related modulation (e.g., cognitive modulation of pain). In clinical settings, baseline connectivity patterns can prospectively predict placebo response magnitude in chronic pain trials and placebo-related symptom change in depression, supporting the premise that intrinsic network organization may shape responsiveness to expectancy manipulations.

Extending these baseline-predictor accounts, recent work in antidepressant placebo models highlights salience network-default mode network (SN-DMN) coupling as a candidate mechanism linking learned expectancies to both acute mood responses and longer-term belief-related symptom trajectories.

In the present study, rsFC will be used to test whether interindividual differences in the intrinsic functional architecture of prefrontal-downstream affective circuitry are associated with affective placebo effects.

In addition, canonical large-scale networks will be examined to characterize intrinsic functional architecture relevant to salience detection, cognitive control, and self-referential or internally oriented processing.

All participants included in this study have completed one of the preceding fMRI placebo studies and agreed to attend a separate MRI session including structural and rsfMRI measurements.

Objectives and hypotheses This rsfMRI study will investigate whether interindividual differences in intrinsic functional coupling are related to primary markers of affective placebo responses.

The lateral PFC will serve as the seed region due to its proposed role in maintaining instructed beliefs and translating treatment expectations into limbic valuation networks.

Canonical large-scale network summaries (SN, FPCN, DMN) will additionally be used as complementary, systems-level descriptors of the broader organizational context in which these targeted pathways are embedded. The following hypotheses are proposed:

  • Interindividual differences in rsFC within prefrontal-emotion-related circuitry are associated with placebo changes in mood.
  • Interindividual differences in rsFC within prefrontal-emotion-related circuitry are associated with placebo changes in task-derived emotional processing.
  • Interindividual differences in rsFC within prefrontal-emotion-related circuitry are associated with placebo changes in expectancy and experienced benefit.
  • Interindividual differences in within-network and between-network rsFC across canonical large-scale networks implicated in cognitive control, salience processing, and internally oriented or self-referential processing are associated with primary outcomes of placebo treatment.

Methods Ethics information The study was approved by the Ethics Committee of the Hamburg Medical Association (PV 7141) and will be conducted in accordance with the Declaration of Helsinki, with written informed consent, financial compensation, and authorized deception as part of the expectancy manipulation.

MRI acquisition parameters MRI data will be acquired on a Siemens Prisma_fit 3T scanner using a 64-channel head/neck coil. Resting-state fMRI will be acquired with a multiband T2*-weighted gradient-echo EPI sequence (TR = 1.33 s, TE = 30 ms, flip angle = 60 degrees, multiband factor = 2, 44 slices, matrix = 76 x 76, voxel size = 3 x 3 x 3 mm). Structural images will be acquired using a high-resolution T1-weighted 3D MPRAGE sequence (TR = 2.53 s, TE = 2.34 ms, TI = 1.10 s, flip angle = 7 degrees, voxel size = 1 mm isotropic, matrix = 256 x 256) for anatomical localization, coregistration, and normalization.

During resting-state acquisition, participants will be instructed to keep their eyes open, fixate on a central cross, remain still, and not perform any explicit task.

Sampling plan The pooled sample is expected to comprise approximately 50 eligible volunteers across the two matched cross-over datasets. An a priori G*Power analysis showed that N = 44 provides approximately 80% power to detect medium effect sizes (r = .40) at alpha = .05.

Analysis plan Resting-state fMRI data will be processed in CONN (RRID: SCR_009550; v25.b, 22 Feb 2026) in combination with SPM12 (RRID: SCR_007037; revision r7771). Structural images will be segmented and normalized using SPM's unified segmentation, and functional images will undergo standard preprocessing, including realignment, slice-timing correction, coregistration, normalization to MNI space, and 8 mm FWHM smoothing. Denoising will use CompCor with white matter and cerebrospinal fluid components, motion regressors and their derivatives, ART-based scrubbing regressors, and band-pass filtering (0.008-0.09 Hz).

General linear models will be used to examine associations between placebo-related outcomes and interindividual differences in resting-state functional connectivity, behavioral indices, and standardized neural measures. Continuous variables will be mean-centered or z-standardized as appropriate, and standardized effect estimates with 95% confidence intervals will be reported.

Resting-state functional connectivity will be quantified as Fisher r-to-z-transformed correlations between BOLD time series and examined using seed-to-voxel and ROI-to-ROI approaches based on prespecified seed and ROI definitions.

Seed-to-voxel maps will be tested using cluster-based inference with a voxel-level threshold of p < .001, uncorrected, and cluster-level FWE correction at p < .05. ROI-to-ROI analyses will assess connectivity between prespecified prefrontal seeds and downstream mesolimbic regions of interest, with significance evaluated using small-volume-corrected FWE control at p < .05.

Complementary systems-level analyses will derive within-network and between-network connectivity summaries for the salience, frontoparietal control, and default mode networks from pairwise Fisher z-transformed edges.

The study is part of the collaborative research center (CRC) SFB/TRR289 and is funded by the Deutsche Forschungsgemeinschaft (DFG, ID: 422744262).

Study Type

Observational

Enrollment (Estimated)

50

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Germany
    • Hamburg
      • Hamburg, Hamburg, Germany, 20246
        • Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

This rs-fMRI study will include healthy volunteers who completed an expectation-manipulation study and agreed to an additional rs-fMRI session.

The sample will be drawn from the ongoing ClinicalTrials.gov-registered study "Expectation Effects on Emotional Processing" (NCT07031804) (Szabo et al., in prep) and a previously collected cohort reported by Mostauli et al. (2025).

In both datasets, participants complete a counterbalanced cross-over fMRI design with sessions approximately one week apart, receiving intranasal saline labeled as "oxytocin" or "saline". In the scanner, participants perform an emotion classification task (Szabo et al., in prep.) or a spatial cueing task with emotional distractors (Mostauli et al., 2025). After finishing the study, participants are invited to an additional MRI session including resting-state fMRI and a T1-weighted scan.

Description

Inclusion Criteria:

  • Aged 18-35 years
  • MRI compatible
  • Medical information and signed declaration of consent
  • Normal or corrected to normal vision
  • German speaking

Exclusion Criteria:

  • No informed consent
  • Current intake of central nervous system active drugs
  • Under influence of alcohol
  • BDI score above 12
  • Significant acute somatic or neurological diseases
  • History of psychiatric or neurological disorders
  • Pregnancy/ breastfeeding
  • Acute nasal diseases or injuries
  • MR-specific exclusion criteria (claustrophobia, pacemaker, non-MR compatible metallic objects)
  • fMRI data with strong artefacts or excessive movement will be excluded from analysis

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Healthy volunteers

This rs-fMRI study will include healthy volunteers who completed an expectation-manipulation study and agreed to an additional rs-fMRI session.

The sample will be drawn from the ongoing ClinicalTrials.gov-registered study "Expectation Effects on Emotional Processing" (NCT07031804) (Szabo et al., in prep) and a previously collected cohort reported by Mostauli et al. (2025).
Other: No intervention
No intervention

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Resting-state functional connectivity measures in prefrontal-emotion-related circuitry
Time Frame: During one separate post-paradigm MRI session lasting approximately 45 minutes, after completion of the preceding placebo study protocol.
Resting-state fMRI will be used to estimate Fisher r-to-z transformed functional connectivity using seed-based and ROI-to-ROI analyses within prefrontal-emotion-related circuitry. These rsFC measures will be tested for associations with participant-level placebo-response indices derived from prior placebo/control sessions.
During one separate post-paradigm MRI session lasting approximately 45 minutes, after completion of the preceding placebo study protocol.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Within-network and between-network resting-state functional connectivity across canonical large-scale networks
Time Frame: During one separate post-paradigm MRI session lasting approximately 45 minutes, after completion of the preceding placebo study protocol.
Resting-state fMRI will be used to derive within-network and between-network connectivity measures for the frontoparietal control, salience, and default mode networks. These measures will be tested for associations with participant-level placebo-response indices derived from prior placebo/control sessions.
During one separate post-paradigm MRI session lasting approximately 45 minutes, after completion of the preceding placebo study protocol.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Stefanie Brassen

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

March 27, 2022

Primary Completion (Estimated)

May 1, 2026

Study Completion (Estimated)

July 1, 2026

Study Registration Dates

First Submitted

March 13, 2026

First Submitted That Met QC Criteria

March 14, 2026

First Posted (Actual)

March 18, 2026

Study Record Updates

Last Update Posted (Actual)

March 23, 2026

Last Update Submitted That Met QC Criteria

March 18, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

  • Z03-ReCAP
  • Project Number 422744262 (Z03) (Other Grant/Funding Number: Deutsche Forschungsgemeinschaft (DFG))

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

With Publication

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ANALYTIC_CODE

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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