How to Calculate and Validate Inter-brain Synchronization in a fNIRS Hyperscanning Study

Area of Science:

• Neuroscience
• Cognitive Science
• Biomedical Engineering

Background:

• Inter-brain synchronization (IBS) quantifies coordinated neural activity between individuals during social interaction.
• Functional near-infrared spectroscopy (fNIRS) hyperscanning enables simultaneous brain recording for studying IBS.
• Wavelet Transform Coherence (WTC) is a common method for assessing IBS in the time-frequency domain.

Purpose of the Study:

• To present a standardized protocol for analyzing IBS using fNIRS hyperscanning.
• To detail the application of WTC for IBS calculation and permutation testing for validation.
• To discuss critical considerations for signal acquisition, preprocessing, and parameter selection in fNIRS hyperscanning.

Main Methods:

• Acquisition of brain signals using fNIRS technology during hyperscanning.
• Calculation of IBS using the Wavelet Transform Coherence (WTC) method.
• Validation of IBS through permutation-based random pairing (trial, partner, condition).

Main Results:

• The proposed protocol provides a clear pipeline for fNIRS hyperscanning IBS analysis.
• WTC effectively reveals time-frequency dynamics of inter-brain synchronization.
• Permutation testing offers a robust method for validating observed IBS findings.

Conclusions:

• The WTC method combined with permutation testing offers a potentially standard pipeline for analyzing IBS in fNIRS hyperscanning.
• This approach enhances the reproducibility and reliability of IBS findings in social neuroscience research.
• Adherence to discussed critical issues ensures robust and meaningful analysis of coupled brain dynamics.