Study Finds Brains Literally "Sync Up" In Conversation

Good communication is a matter of getting "in sync" with others, as you've probably noticed when you've seen people match their steps perfectly as they walk, and imitate each other's gestures as they talk, and use each other's phrases and grammar. Last week, this paper reported  this kind of coordination in the most important place of all: When people converse, it reports, regions of their brains synchronize their activity. "Neural coupling," they argue, is a key part of communication.


Uri Hasson, Lauren Silbert and Greg Stephens recorded Silbert telling a 15-minute story while an MRI scanner recorded changes in activity levels in various regions of her brain. The researchers then played the recording to 11 volunteers while their brains were MRI-ed. As they listened, the paper reports, their brains' patterns of activity matched Silbert's.

The work is a nice departure from models that look for activity in "the brain," because, of course, communication doesn't take place in isolation. It also challenges the notion that listening and talking are neatly separated activities: "neural coupling" took place in both "comprehension" and "production" regions of the listeners' brains.

Especially interesting, as Michael Balter points out, were the regions in which the listeners went first: As they heard the story, their brains fired in a pattern that matched Silbert's, but hers came a moment later. They were, it seems, anticipating what she would say, priming themselves to hear what they expected. The better the match between Silbert's brain activity and these "predictive anticipatory responses" in a listener, the better the listener understood the story.

Thanks to some ingenious experiments by Sir Frederic Charles Bartlett in the 1930's, we know that listeners often "fill in" details of what they are hearing (and that their memories of the speaker don't distinguish between what they actually heard and what they supplied themselves). When students retold a folk tale he had given them to read, Bartlett found, they added some details (for instance, where the story read ``that Indian has been hit,'' some students recalled an Indian being killed, others an Indian being hit by an arrow). They also changed some unfamiliar facts (making the story's Indians "row" their canoe like proper English undergraduates). You can try it yourself: Read the story here, then re-tell it in a couple of days from memory, then compare what you've written or recorded to the original.

Yet these people felt sure that their memories of the story were accurate. They didn't notice the difference between what they had read and what they had supplied themselves. Why such confidence? Bartlett proposed that the mind understands the world by means of "schemas"—mental maps that relate actions and objects to each other. Once learned, the schema works rather like a form with blanks to be filled in. Once I know you're talking about Indians and canoes, I "fill in" arrows and moccasins even if you don't mention them (and I if you bring in samurai swords I might miss it, because those don't fit the schema).

Perhaps Hasson et al.'s paper, published in the Proceedings of the National Academy of Sciences, has touched on the physiological correlates of Bartlett's schemas. Perhaps, too, it has pointed to the physiological basis for the pleasure people take in synchronized activities—singing together in tune, marching together in time, doing the "wave." If "neural coupling" is essential to understanding others, then it would make sense that people would find it pleasurable and seek to create it.

Stephens, G., Silbert, L., & Hasson, U. (2010). Speaker-listener neural coupling underlies successful communication Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1008662107

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Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.

The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.

The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.

Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.

"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."

University of Colorado Boulder

Christopher Lowry

This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.

Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.

The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.

Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.

What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.

"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."

Check out the study published in the journal Psychopharmacology.