Know Your Brain: Superior Temporal Sulcus — Channeling The “Social Brain”

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We like to think we came up with that idea — pride ourselves on the privacy of our thoughts and dreams, and perhaps a little on our own ability to embellish. We like to think of genius as something that comes in sudden bursts of inspiration — magic that only we can untap for ourselves, and that all the great thinkers were loners who lived in their own heads. As usual, science has other ideas.

No one is an island — the reason you should ask not for whom the bell tolls, and nothing further reinforces the notion like modern neuroscience. We do not develop in isolation, nor can we thrive in it. Your brain is a prime example. As we grow, the neurons throughout our brains will forge over 100 trillion connections, or synapses, as we meet and interact with new people and acquire new skills.

Your brain is the original social network — its own functioning dependent on the community it grows up in. Long before you develop the ability to speak, your brain is working to imitate the sounds it absorbs — with the help of the superior temporal sulcus, situated within the brain’s temporal lobe, the part of your brain involved in processing visual memory and emotion. We are, by nature, collaborators.

The brain’s “social river,” the superior temporal sulcus (STS) is a long, narrow groove situated just above the ears on the surface of the brain, rising just above the crown of the head. It collects information from neurons throughout the brain — think of these as small rivulets emptying into it — a continuous flow of sounds and images. Studies using functional MRI technology reveal that brain activity peaks in the STS upon hearing human voices — which it deciphers from background noises.

It’s also why you can tell apart the voices of friends and strangers on your phone or talking just outside your door. It also allows you to distinguish faces from objects that aren’t human and piece together words of a coherent sentence — why you can process those words of a novel on your Kindle and understand the plot, and recognize spam email better than your inbox filter. In turn, the STS is also used to detect social cues — to interpret and mirror the emotions of those around us, crucial functions that only adapt due to our day-to-day interactions with other people.

How much influence do these external forces have on shaping the brain? A study published by Proceedings of the Royal Society B: Biological Sciences suggested that people who made more friends on Facebook had larger brains than their peers. The researchers were not able to determine if it was sending out a flurry of friend requests that bulked up their brains, or if those with a larger than average brain size just tend to seek out human interaction more.

A subsequent study published in Science followed 23 different macaques. One group was assigned to live on their own with a companion, or in groups ranging from three to seven other primates. The study found that monkeys living in the larger groups had higher volumes of gray matter in regions for processing social information.

“The superior temporal sulcus, or the amygdala, are implicated in humans and macaques, suggesting that the brain networks involved in processing social information in humans has evolved from a network that was already performing computations related to social cognition in rhesus macaques,” said Jerome Sallet, a University of Oxford researcher who conducted the study. Primates tended to thrive better in settings where they came to interact and rely on each other.

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A magazine dedicated to the brain.

We believe that neuroscience is the next great scientific frontier, and that advances in understanding the nature of the brain, consciousness, behavior, and health will transform human life in this century.

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