

February 28, 2017

A cartoon image of brain “coupling” during communication (credit: Drexel University)


(KurzweilAI recently covered research with a fNIRS brain-computer interface that allows completely locked-in patients to communicate.)

A fNIRS headband (credit: Wyss Center for Bio and Neuroengineering)

Mirroring the speaker’s brain activity

The researchers found that a listener’s brain activity (in brain areas associated with speech comprehension) mirrors the speaker’s brain when he or she is telling a story about a real-life experience, with about a five-second delay. They also found that higher coupling is associated with better understanding.

The researchers believe the system can be used to offer important information about how to better communicate in many different environments, such as how people learn in classrooms and how to improve business meetings and doctor-patient communication. They also mentioned uses in analyzing political rallies and how people handle cable news.

“We now have a tool that can give us richer information about the brain during everyday tasks — such as person-to-person communication — that we could not receive in artificial lab settings or from single brain studies,” said Hasan Ayaz, PhD, an associate research professor in Drexel’s School of Biomedical Engineering, Science and Health Systems, who led the research team.

Traditional brain imaging methods like fMRI have limitations. In particular, fMRI requires subjects to lie down motionlessly in a noisy scanning environment. With this kind of setup, it’s not possible to simultaneously scan the brains of multiple individuals who are speaking face-to-face. Which is why the Drexel researchers turned to a portable fNIRS system, which could probe brain-to-brain coupling question in natural settings.


The researchers targeted the prefrontal and parietal areas of the brain, which include cognitive and higher order areas that are involved in a person’s capacity to discern beliefs, desires, and goals of others. They hypothesized that a listener’s brain activity would correlate with the speaker’s only when listening to a story they understood (the English version). A second objective of the study was to compare the fNIRS results with data from a similar study that had used fMRI to compare the two methods.

They found that when the fNIRS measured the oxygenation and deoxygenation of blood cells in the test subject’s brains, the listeners’ brain activity matched only with the English speakers.* These results also correlated with the previous fMRI study.

The researchers believe the new research supports fNIRS as a viable future tool to study brain-to-brain coupling during social interaction. One can also imagine possible invasive uses in areas such as law enforcement and military interrogation.

The research was published in open-access Scientific Reports on Monday, Feb. 27.

* “During brain-to-brain coupling, activity in areas of prefrontal [in the speaker] and parietal cortex [in the listeners] previously reported to be involved in sentence comprehension were robustly correlated across subjects, as revealed in the inter-subject correlation analysis. As these are task-related (active listening) activation periods (not resting, etc.), the correlations reflect modulation of these regions by the time-varying content of the narratives, and comprise linguistic, conceptual and affective processing.” — Yichuan Liu et al./Scientific Reports)

Abstract of Measuring speaker–listener neural coupling with functional near infrared spectroscopy
