Systemic physiology augmented functional near-infrared spectroscopy hyperscanning: a first evaluation investigating entrainment of spontaneous activity of brain and body physiology between subjects

• Published in: Neurophotonics (Print) Vol. 9; no. 2; p. 026601
• Main Authors: Guglielmini, Sabino, Bopp, Gino, Marcar, Valentine L., Scholkmann, Felix, Wolf, Martin
• Format: Journal Article
• Language: English
• Published: United States Society of Photo-Optical Instrumentation Engineers 01.04.2022; SPIE; S P I E - International Society for
• Subjects: Blood pressure; Brain research; Cognition & reasoning; Entrainment; Eye; Eye contact; Hemodynamics; Infrared spectroscopy; Medical imaging; Medical research; Neuroimaging; Neurosciences; Physiology; Simulation; Social interaction; Spectrum analysis; Synchronization; Technical Notes; Time series; Visual communication; Switzerland; United States > US; Berlin Germany; Massachusetts; Germany; cross-brain coherence; systemic physiology augmented functional near-infrared spectroscopy hyperscanning; functional near-infrared spectroscopy; SPA-fNIRS; hyperscanning; eye contact; systemic physiology augmented functional near-infrared spectroscopy; interpersonal brain synchronization
• ISSN: 2329-423X; 2329-4248
• DOI: 10.1117/1.NPh.9.2.026601

Significance: Functional near-infrared spectroscopy (fNIRS) enables measuring the brain activity of two subjects while they interact, i.e., the hyperscanning approach. Aim: In our exploratory study, we extended classical fNIRS hyperscanning by adding systemic physiological measures to obtain systemic physiology augmented fNIRS (SPA-fNIRS) hyperscanning while blocking and not blocking the visual communication between the subjects. This approach enables access brain-to-brain, brain-to-body, and body-to-body coupling between the subjects simultaneously. Approach: Twenty-four pairs of subjects participated in the experiment. The paradigm consisted of two subjects that sat in front of each other and had their eyes closed for 10 min, followed by a phase of 10 min where they made eye contact. Brain and body activity was measured continuously by SPA-fNIRS. Results: Our study shows that making eye contact for a prolonged time causes significant changes in brain-to-brain, brain-to-body, and body-to-body coupling, indicating that eye contact is followed by entrainment of the physiology between subjects. Subjects that knew each other generally showed a larger trend to change between the two conditions. Conclusions: The main point of this study is to introduce a new framework to investigate brain-to-brain, body-to-body, and brain-to-body coupling through a simple social experimental paradigm. The study revealed that eye contact leads to significant synchronization of spontaneous activity of the brain and body physiology. Our study is the first that employed the SPA-fNIRS approach and showed its usefulness to investigate complex interpersonal physiological changes.