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Mechanisms of open and hidden placebo in stroke recovery: targeting neuroplasticity insights of the placebo effect - study protocol for a controlled, parallel, randomised clinical trial

Ortega-Márquez J, Camargo L, Gianlorenço AC, Sosa W, Black-Schaffer R, Wang QM, Fregni F

BMJ open, 2026

56 participants

Abstract

Introduction: Stroke stands as one of the worldwide leading causes of disability, highlighting the need to develop new therapies. Although placebo effects in motor recovery have been reported to produce clinically meaningful improvements, the neural substrates underlying these effects, particularly across different modalities such as open-label and hidden placebo, remain unclear. This study aims to characterise the neurophysiological signatures of hidden and open placebo during motor-cortex stimulation in chronic stroke survivors and its correlation to motor recovery.

Methods and analysis: This single-centre, parallel-group, controlled, randomised clinical trial will enrol 56 adults (≥6 months post-stroke) with upper-limb hemiparesis. Participants are block-randomised (2:2:2:1) to (i) open-label placebo tablets, (ii) hidden sham repetitive transcranial magnetic stimulation (rTMS), (iii) no intervention or (iv) active low-frequency (1 Hz) rTMS over the contra lesional primary motor cortex. The primary endpoint is change in frontal alpha asymmetry (FAA) on high-density electroencephalogram from baseline to 2 weeks. Secondary endpoints include β-band premotor-to-M1 coherence and Fugl-Meyer Upper Extremity scores. Exploratory outcomes include additional motor performance measures (Jebsen-Taylor Hand Function Test and Nine-Hole Peg Test), corticospinal excitability (single-pulse and paired-pulse TMS) and patient-reported measures (mood, expectancy and behavioural…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 56 participants or records.

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