By Felipe Orihuela-Espina and Joy Hirsch
Hyperscanning is concerned with the concurrent neuroimaging of more than one subject simultaneously. Understanding the synchronized activities of brains has important implications to understanding our social interactions whether in cooperative or competitive settings. Neuropsychology and social neuroscience are the obvious scientific field winners.
The first recorded paper on hyperscanning according to PubMed was published only in 2002 . Even today, only slightly over 100 papers have been published on hyperscanning (see Figure 1) but the steady growth is a clear statement of its relevance and the interest it raises. And a recent review  shows that a good amount of these studies comes from our fNIRS. Of course, it is not that scientists have missed the importance on understanding social interactions for so long. It was just a technological limitation. The interest on the topic was latent, just waiting for in-vivo neuroimaging modalities to mature. But as with all good ideas, its time has come.
These early studies have faced important challenges inherent to the multiple individual setups: higher costs, synchronization of signals, interscanner variability, unsuitability of traditional analytical models, latencies, new sources of biases, increment in dataset sizes proportional to the number of individuals in the experimental unit, and so on. It should be expected that as the field advances these difficulties will be alleviated. Early studies have been mostly confined to just dyads i.e. the experimental unit being sized two individuals, but there is no physical limit to bigger units. Wavelets, coherence, graph theory, physio-psychological interactions and causal analysis are emerging as the initial preferred analytical options, but it is still too early to agree on a de facto analytical standard.
Nevertheless, the early studies are already proving to be pure gold. When facing a certain task, such as eye-to-eye contact or verbal dialogue as in exchanges of talking and listening, our brains behave differently when we are interacting with someone else. This has segregational as well as synchronous effects [3,4]. Segregational aspects manifest in terms of the recruitment of specialized, within brain, neural systems that would otherwise be spared in the face of the same stimulus when no social interaction is involved. Synchronization aspects involve the neural processors of the experimental subunits i.e. the individuals are activated in synchrony alike a functional choreography. The new evidence provided by hyperscanning studies is confirming these hypotheses and opens a new direction of investigation for the “Neuroscience of two or more”.
Since we are political animals, which is just a different way of saying we are inherently social, hyperscanning as the natural sensing scheme for social neuroscience has direct and profound implications to our lives; education, parenting, economics, communication, and a long etcetera. Stay hyper-tuned!
To know more:
- Montague PR et al (2002) NeuroImage; 16, 1159-1164. doi: 10.1006/nimg.2002.1150
- Wang MY et al (2018) Quant Imaging Med Surg; 8(8):819-837. doi: 10.21037/qims.2018.09.07
- Hirsch, J et al (2017) NeuroImage; 157, 314-330. doi: 10.1016/j.neuroimage.2017.06.018
- Hirsch, J et al (2018) Social Cognitive and Affective Neuroscience;13,907-920. doi: 10.1093/scan/nsy070.