The effect of interbrain synchronization in gesture observation: A fNIRS study

Abstract

Introduction Gestures characterize individuals' nonverbal communicative exchanges, taking on different functions. Several types of research in the neuroscientific field have been interested in the investigation of the neural correlates underlying the observation and implementation of different gestures categories. In particular, different studies have focused on the neural correlates underlying gestures observation, emphasizing the presence of mirroring mechanisms in specific brain areas, which appear to be involved in gesture observation and planning mechanisms. Materials and methods Specifically, the present study aimed to investigate the neural mechanisms, through the use of functional Near‐Infrared Spectroscopy (fNIRS), underlying the observation of affective, social, and informative gestures with positive and negative valence in individuals' dyads composed by encoder and decoder. The variations of oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations of both individuals were collected simultaneously through the use of hyperscanning paradigm, allowing the recording of brain responsiveness and interbrain connectivity. Results The results showed a different brain activation and an increase of interbrain connectivity according to the type of gestures observed, with a significant increase of O2Hb brain responsiveness and interbrain connectivity and a decrease of HHb brain responsiveness for affective gestures in the dorsolateral prefrontal cortex (DLPFC) and for social gestures in the superior frontal gyrus (SFG). Furthermore, concerning the valence of the observed gestures, an increase of O2Hb brain activity and interbrain connectivity was observed in the left DLPFC for positive affective gestures compared to negative ones. Conclusion In conclusion, the present study showed different brain responses underlying the observation of different types of positive and negative gestures. Moreover, interbrain connectivity calculation allowed us to underline the presence of mirroring mechanisms involved in gesture‐specific frontal regions during gestures observation and action planning.

Filling in the gaps: observing gestures conveying additional information can compensate for missing verbal content

“…Therefore, the combination of gesture's ability to both direct visual attention and simultaneously add information to accompanying speech appears to be important in how gesture enhances learning. Similarly, neuroscience research has shown that different areas of the brain not associated with attention, such as the motor cortex, activate when gestures are observed (e.g., Fronda & Balconi, 2020, further highlighting that the relationship between gesture and speech could impact learning.…”

Intra-Brain Connectivity vs. Inter-Brain Connectivity in Gestures Reproduction: What Relationship?

“…Namely, for each dyad, one individual (the encoder) was asked to observe and reproduce the gesture seen in the video toward his/her partner (the decoder), who was, instead, asked to observe the reproduced gesture. The task presentation was divided into three blocks, each composed of randomized stimuli, with the following structure: an initial blank screen (2-second duration), a short description of the context of observed interactions (4-second duration), the gesture presentation video (3-second duration), a blank inter-stimulus (4-second duration), and a final “go” signal to reproduce the gesture ( Figure 1 A) [ 36 , 37 , 38 , 39 ]. The videos presented gestures of different types (namely, social, affective, and informative ones), and of different valence (namely, positive and negative).…”

“…Finally, the videos reproducing informative gestures aimed to describe an informative situation without social or emotional content. The positive or negative valence for informative gestures was attributed to the context shown before the video [ 36 , 37 , 38 , 39 ].…”

“…The implementation of the task was preceded by a preliminary phase dedicated to stimuli validation, which involved 14 judges (M age = 28.34, SD age = 0.04) who were asked to evaluate, using a seven-point Likert scale, the emotional impact, familiarity, social meaning, concreteness, complexity, commonality, and use frequency of each gesture. The definition of stimuli categories and their primary features were tested via statistical analysis [ 36 , 37 , 38 , 39 ].…”

“…The assumption of a two-person perspective, and the simultaneous recording of two participants’ brain activity using EEG in hyperscanning, allow researchers to examine hyperbrain functional networks, which include functional connectivity and allow for obtaining information about mechanisms of intra-brain and inter-brain connectivity [ 35 ]. As such, in this paper, individuals’ intra-brain connectivity patterns were calculated during the execution of different gestures conveying emotional, social, and informative contents [ 36 , 37 , 38 , 39 ]. Specifically, the present study aimed to investigate the relationship between intra-brain and inter-brain connectivity in dyads of interacting individuals (an encoder, who executed the gesture, and a decoder, who received the gesture) during the execution of different types of gestures (affective, social, and informative ones), both positively and negatively connoted.…”