Inter-Brain Synchrony in Open-Ended Collaborative Learning: An fNIRS-Hyperscanning Study
July 21st, 2021
The protocol for conducting fNIRS hyperscanning experiments on collaborative learning dyads in a naturalistic learning environment is outlined. Further, a pipeline to analyze the Inter-Brain Synchrony (IBS) of oxygenated hemoglobin (Oxy-Hb) signals is presented.
This protocol reveals inter-brain synchrony in the collaborative dyads in the naturalistic environment by the fNIRS hyperscanning technique. The significant advantage of this technique is it allows investigation of real-time dynamics of two or more interacting brains. Before beginning the experiment, start the near infrared spectroscopy system for achieving a stable operating temperature, then adopt an elastic swimming cap to place the optode-holder grid and prepare the NIRS caps as described in the text manuscript.
For a channel with insufficient signals, use the lighted fiber optic probes to move the hair under the probe's tip to one side. Once the operating temperature stabilizes, ensure that the trigger receiver is active and set the measurement mode to event-related measurement. Prepare the lighted fiber optic probe to move hair aside.
Instruct the participants regarding the details of NIRS measurement methods and not to look directly into the laser beams as the laser beam may be harmful to the participant's eyes. Make the participants sit face to face to make sure they can see each other directly and adjust the chair-to-table distance to make the participants sit comfortably. Turn on the laser button, put the four optical fiber bundles loosely on the holder's arms without contact with the participants or chairs and place the cap with the probe sets on the participants'heads, ensuring that the three-by-five probe sets cover the forehead of the participant and the four-by-four probe sets cover the left temporoparietal cortex, then carefully push each spring-load probe further into the probe socket so that the probe's tip touches the scalp of the participant.
Then allow two participants to co-learn the learning materials with five minutes rest state, which serves as the baseline. First, to check the quality of the signal, click the auto gain in the probe set monitor window of the functional NIRS machine, and then mark the channel's poor signal in yellow and the sufficient signal in green and repeat this procedure until all the channels are marked green. After the experiment, click on the Text File Out to export the raw light intensity data and save the data as a text file.
Use the three-dimensional digitizer to determine the locations of emitters, receivers, and other references for each participant, then obtain the MNI coordinates of the recording channels using the commercially available numeric computing platform. The data from each participant in each channel were analyzed. The optodensity in channel 33 for a certain dyad was visualized.
The data were extracted using the wavelet-based motion artifacts removing method, alone and along with the principal components analysis. The difference between the curves suggests that PCA is efficient in removing non-neural signals. The wavelet transform coherence matrix was visualized.
The color map varied from blue to yellow, representing inter-brain synchrony values ranging from zero to one, where one denotes the largest coherence between two signals and zero denotes no coherence. In addition, significant coefficients were also obtained, the strong coherence around one hertz representing the dyad's cardiac rhythm coherence. The comparison between the observed T value and the distribution of random T value shows significant results in identified FOI.
It's important to make sure the probe set covers the region of interests and try to reduce the deviation.
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Overview
This study outlines a protocol for conducting functional near-infrared spectroscopy (fNIRS) hyperscanning experiments to investigate inter-brain synchrony during collaborative learning in a naturalistic setting. The analysis focuses on oxygenated hemoglobin (Oxy-Hb) signals to assess real-time dynamics of two interacting brains.
Key Study Components
Area of Science
- Neuroscience
- Collaborative Learning
- Brain Connectivity
Background
- Functional near-infrared spectroscopy (fNIRS) is used to study brain activity.
- Inter-brain synchrony (IBS) helps understand collaborative interactions.
- Naturalistic environments are essential for studying real-life interactions.
- The protocol elaborates on equipment setup and participants’ positioning.
Purpose of Study
- To provide a method for examining IBS in learning dyads.
- To detail the fNIRS setup for capturing Oxy-Hb signals.
- To establish a baseline for cognitive engagement during collaborative learning.
Methods Used
- The fNIRS hyperscanning technique was employed during teamwork activities.
- Participants were positioned face-to-face to enhance interaction.
- Data gathering involved ensuring stable fNIRS operation and participant comfort.
- Signal quality was assessed and artifacts were removed using wavelet methods.
Main Results
- Inter-brain synchrony was visualized, demonstrating coherence during collaboration.
- Data analysis highlighted strong coherence at around one hertz related to cardiac rhythm.
- The protocol affirmed the efficacy of PCA in filtering non-neural signals.
Conclusions
- This study validates a comprehensive method to assess IBS in collaborative contexts.
- The findings support understanding of cognitive processes during social interactions.
- This protocol can facilitate further exploration of neural dynamics in learning environments.
Frequently Asked Questions
Executive Industry Relevance
Inter-brain synchrony measurement via fNIRS hyperscanning provides a neurobiological index for assessing real-time collaborative dynamics, offering mechanistic insights into social learning processes. This approach supports target validation in neuroscience by enabling quantitative evaluation of neural coupling during interactive tasks, which can inform biomarker development for cognitive and behavioral disorders. The standardized pipeline enhances reproducibility and cross-lab comparability, aligning with open-science principles critical for preclinical de-risking and translational continuity.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses related to social cognition and neural connectivity mechanisms.
- Operational Value: Provides a reproducible method for functional target validation using inter-brain synchrony as a phenotypic readout.
- Predictive Value: Supports mechanistic de-risking by quantifying neural coherence as a biomarker of collaborative engagement.
Screening & Assay Development
- Assay Readiness: Prepares validated biological systems (dyadic brain networks) for downstream screening of compounds affecting social behavior.
- Quantitative Output: Delivers oxygenated hemoglobin-based synchrony metrics enabling dose-response analysis in preclinical models.
- Platform Scalability: Standardized fNIRS hyperscanning pipeline supports reuse across laboratories and study designs.
Translational & Preclinical Research
- Disease Relevance: Applicable to disorders with social dysfunction (e.g., autism, schizophrenia) where inter-brain synchrony may serve as a translational biomarker.
- Preclinical Continuity: Bridges discovery-phase neural mechanism identification with preclinical validation of pro-social compounds.
- Risk-Adjusted Advancement: IBS metrics inform go/no-go decisions by providing objective neural correlates of target engagement.
Pipeline & Workflow Integration
The fNIRS hyperscanning method integrates into the discovery continuum from target hypothesis testing through lead identification to preclinical validation, particularly for CNS targets modulating social neural circuits.
- Discovery Biology: Supports hypothesis testing of neural pathways involved in social learning and interaction.
- Screening: Enables assay standardization and reproducibility for evaluating compounds that modulate inter-brain synchrony.
- Analytics: Provides wavelet coherence and principal component analysis outputs for quantitative comparison of neural dynamics across conditions.
- Translational Research: Connects Oxy-Hb synchrony measures to preclinical models of social cognition via biomarker alignment.
- Enterprise Reuse: Establishes a reusable neurophysiological platform for cross-functional teams studying social brain networks.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation by reducing ambiguity in social neural mechanism interpretation.
- Operational Value: Ensures standardization, reproducibility, and scalability of hyperscanning protocols across sites.
- Strategic Value: Improves go/no-go decision quality through objective neural synchrony readouts, reducing late-stage attrition in CNS programs.
- Portfolio Impact: Enables risk-adjusted prioritization of compounds based on mechanistic biomarker data from interactive paradigms.
Implementation Considerations
- Requires expertise in neuroimaging, experimental design, and signal processing for fNIRS data.
- Dependent on stable near-infrared spectroscopy systems and motion artifact correction capabilities (e.g., wavelet-based methods, PCA).
- Necessitates cross-team standardization of probe placement, signal quality checks, and data export procedures.
- Adaptation across model systems must account for species-specific neuroanatomy and hemodynamic response characteristics.
- Practical limitations include susceptibility to motion artifacts and environmental light interference, as noted in source material.
