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

Abstract

. 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.

Optical imaging and spectroscopy for the study of the human brain: status report

“… 144 – 146 SPA-fNIRS can also be used in a hyperscanning setting; the first SPA-fNIRS hyperscanning study was recently published. 147 …”

“…[144][145][146] SPA-fNIRS can also be used in a hyperscanning setting; the first SPA-fNIRS hyperscanning study was recently published. 147 In general, SPA-fNIRS is an excellent approach to enable a deeper understanding of the fNIRS signals and prevent misinterpretation. It allows one to gain insight into what causes the changes in fNIRS signals.…”

Systemic physiology augmented functional near-infrared spectroscopy: a powerful approach to study the embodied human brain

“…Recently, the first SPA-fNIRS hyperscanning studies were performed, showing the usefulness and potential of the addition of measuring systemic physiological signals along fNIRS neuroimaging to investigate the functional body-to-body body-to-brain and brain-to-brain coupling in interacting subjects. 135 , 136 The term “SPA-fNIRS hyperscanning” was introduced for this methodology. 136 …”

“…Since the interplay between these two types of networks is currently an open research question, 140 SPA-fNIRS could possible provide novel answers to this question. In addition, the extension of the fNIRS hyperscanning approach 133 to SPA-fNIRS hyperscanning, as recently demonstrated, 135 , 136 will allow one to explore the physiological functional coupling between interacting subjects in a new way.…”

HyperOptoNet: a MATLAB-based toolbox for inter-brain neuronal synchrony analysis using fNIRS hyperscanning

“… 13 , 14 Recently researchers could better measure the inter-brain coupling associated with social interactions, and many studies about educational communication, a face-to-face game, improving cognitive performance, and body physiology between subjects have been reported using the fNIRS-based hyperscanning technology. 7 – 9 , 15 , 16 …”