Lulled in the countless chambers of the brain, our thoughts are linked by many a hidden chain; awake but one, and in, what myriads rise!”
As we delve further into the brain, one of science’s great frontiers, we are always surprised, but 18th century English poet Alexander Pope was more right than he realized.
With the Earth now stuffed with seven billion people, the latest revelation about the brain is that it makes more sense to be a social animal than a lone ranger. The more people you know, the more your brain grows, suggests a paper in the latest edition of the journal Science.
When Jerome Sallet and colleagues studied 23 macaque monkeys—living alone, with another and in groups of three to seven—they found monkeys in larger groups displayed changes in parts of their brains processing social information. Macaque and human brains are close enough to draw some inferences.
First, the fact that the brain grows— Sallet prefers to use the word “plasticity” to refer to structural and functional changes in a brain reacting to a new environment—even during adulthood. Not only could new skills induce brain changes (for instance, if you learn how to juggle or, in the case of a monkey, if it’s taught to use a tool), your social environment could too.
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Second, the findings back previous research that a social environment and its complexities spark growth in certain brain circuits, not the entire brain.
Third, the study suggests similarities between humans and macaques in some regions in the temporal and prefrontal cortex, both involved in social cognition.
The researchers also found correlations between social ranking and the size of specific regions in the brain, which could mean that more social animals could do better in life.
If some of this sounds familiar, it’s because we have known for long that no human is an island. Social cognitive theory dates back to the 1940s and explains that people develop their skills and personalities by watching what others do.
The latest study delves into specifics. The scientists mainly observed changes in the temporal cortex, whose neurons are known to be sensitive to faces and body movements, and the amygdala, know to be involved in emotional responsiveness.
The biology of these changes, however, is still a hotly debated mystery.
A brain changes and grows by sprouting new blood vessels, new or larger cells, greater blood flow. But vast areas of our grey matter are, well, grey areas. While all these changes occur, there is little evidence of neurogenesis—growth of new neurons, the specialized cells that drive the human nervous system, or, what we know as our mental life.
The mysteries are endless. For instance, among the cells that do grow are glial cells, which are 10 times as many as there are neurons. For decades, glial cells were regarded the dark matter of the brain, much like the dark matter of the universe. About a trillion glia make up 90% of the brain. They are now known to guide the brain’s development and sustain while we are alive. Glia speak a chemical language of their own, not the electricity that is the language of neurons and thought. We do not yet understand that language, but now know it is part of the brain’s filing process as we learn and form memories.
There is much we learn about the human brain from other species. The ability of neurons to rewire themselves was first revealed more than 60 years ago. Carl Zimmer writes in an April issue of Discover magazine: “In the 1940s, the Nobel prize–winning neurobiologist Roger Sperry performed some of the most important brain surgeries in the history of science. His patients were newts. Sperry started by gently prying out newts’ eyes with a jeweller’s forceps. He rotated them 180 degrees and then pressed them back into their sockets. The newts had two days to recover before Sperry started the second half of the procedure. He sliced into the roof of each newt’s mouth and made a slit in the sheath surrounding the optic nerve, which relays signals from the eyes to the brain. He drew out the nerve, cut it in two, and tucked the two ragged ends back into their sheath. If Sperry had performed this gruesome surgery on a person, his patient would have been left permanently blind. But newts have a remarkable capacity to regrow nerves. A month later, Sperry’s subjects could see again.”
So, does the latest study reveal social monkeys, or humans, are smarter?
When I asked Sallet, he provided a nuanced answer: “Living in social groups may not make you smarter in the broad sense, but you may become more skilled at interpreting or using social cues.” The bottom line—larger the social group, the more complex the information the brain must process, and the more your brain grows.
Samar Halarnkar is editor-at-large, the Hindustan Times and Mint. This is a fortnightly column that explores the cutting edge of science and technology. Comments are welcome at firstname.lastname@example.org