At a dinner party, are people hanging onto your words or cutting you off mid-sentence? Recent research suggests that differences in social standing may lie in neurons—and how well they function—in the front of your brain
Fei Wang, a graduate student studying under Hailan Hu at the Chinese Academy of Sciences, led the study looking at how brain function affected social standing in mice. What she found is that mice with especially efficient neurons in a part of their brain called the medial prefrontal cortex (mPFC)—a region, just behind the forehead, known to be involved with social behavior and decision-making—reliably ranked near the top of the social hierarchy.
Human studies of the mPFC show that it plays a role in social cognition, such as forming judgments of other people or assessing their intentions. A rat study found that damage to the mPFC led to a downturn in social standing. Despite the link between mPFC function and social standing, we had little understanding of what was going on in this brain region that determined social rank. Wang's study suggested it was all in the neurons. She found that mice with the highest-functioning neurons in their mPFC climbed to the top of the social ladder.
Wang measured social standing by putting two male mice into a narrow tube facing each other. Without enough room to get around each other, one of the mice was forced to back out of the tube so the other could get out going forward. Wang considered backing out a sign of submission, so the mouse that went forward was the dominant mouse.
Wang validated the tube test by showing that social status had a hierarchy, so if mouse A outranked mouse B, and mouse B outranked mouse C, mouse A also outranked mouse C. As further proof, mice that went forward in the tube were also dominant in other measures of status, such as access to food or females for mating. These were the Mickeys that wound up with Minnie Mouse.
Once Wang had established the social hierarchy among the mice, she tested the neurons in the mPFC. She measured the neuron's function by the strength of the electrical output it created when it received a signal from a neighboring neuron. The brain understands the world and makes decisions based on the ability of millions of neurons to communicate. Neurons communicate primarily through chemical signals. When a neuron receives a chemical signal, it responds by a change in electrical output, but the strength of this output can vary by neuron. Wang found that the highest ranking mice, the Mickeys, also had the largest electrical output in their mPFC neurons. The old image of the genius with a light bulb above his head might bear some truth.
Why would high electrical output of mPFC neurons relate to social status? Wang et al. suggest that the high electrical output could result in these neurons sending a stronger message to other brain regions. In other words, the mPFC doesn't control social behavior by itself, but it works by communicating with other regions. The mPFC makes decisions about what's socially appropriate and passes that information on. The brain that best transmits information on what's socially appropriate ends up making the savviest decisions, and the owner of that brain becomes the highest ranking mouse, top dog, or queen bee.
That's fascinating in its own right, to think that the electrical signal in a group of neurons could have such a large effect on our lives. Animals higher in the hierarchy tend to live longer, have better health and more access to resources. Social hierarchy depends on cognitive traits, including the recognition of status, the ability to learn social norms and the ability to detect when norms are violated. All of these contribute to an individual's place within a group.
So if you want the catbird's seat at dinner, you can get there with a caucus of fast-firing neurons that help make keen social decisions. Pretending to eat baby corn off the cob might win you points in some circumstances or cause the group to cringe in others, so know your audience before daring something so goofy.
Here comes the twist to Wang's study. The efficiency of these neurons can be changed, and this will have immediate impact on your social rank. Wang et al. injected a virus which infiltrated the DNA of the mice, resulting in a specific change in the electrical output of the neurons in the mPFC. High-ranking mice infected with a virus which impaired their channels went down in rank. Within a group of 4 mice, they went from top-mouse to bottom, the mouse that consistently yielded in the tube. Conversely, when a low-ranking mouse was injected with a virus which improved its channel function, it began climbing the social ladder. Within a day, it was going forward in the tube against mice that it yielded to just a day before.The simple change in the brain dramatically changed the social structure of this group.
The results are as interesting as they are eyebrow-raising. Could such a small, specific group of neurons really have such a dramatic impact on our social standing? It seems hard to believe that a peppercorn-sized region of our brain makes all the difference between if we're sitting at the center of the dinner-table or relegated to the end.
Yet, the brain has proven to have regions with remarkably specific functions and dramatic results when this region is altered. For example, prosopagnosia, a disorder marked by difficulty recognizing faces, results from damage to the fusiform gyrus, a tiny region in the rear of the brain. Prosopagnostics can recognize objects and identify people by the sound of their voice, but faces do not register an identity. Perhaps the mPFC has similarly specific function with regard to social rank.
Although it's too early to conclude that humans can similarly improve their social status by tweaking their mPFC, Wang's study provides some tantalizing clues as to what might underlie the fundamental structure of our social lives, and it all rests in the function of a specific set of neurons in the front of our brain. So, if you want to be the recipient of the toast at the next dinner engagement, you might want to tune up your brain cells. And try not to spill your glass of Malbec on the host's cream-colored cashmere sweater.
Wang F, Zhu J, Zhu H, Zhang Q, Lin Z, Hu H. Bidirectional Control of Social Hierarchy by Synaptic Efficacy in Medial Prefrontal Cortex. Science 4 November 2011:
Vol. 334 no. 6056 pp. 693-697