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October 26, 2017

Penn experiments discover brain region key to driving behavioral change

Creatures of habit have a hard time switching things up when they've mastered a reliable routine to find sustenance and pleasure in life.

But when change inevitably arrives, bringing crisis or diminishing returns, what is it that motivates us to brave considerable risk for the sake of survival, or simply a better lot in life?

Researchers at the University of Pennsylvania teamed up with colleagues at Yale, Columbia and Duke universities to find a biological answer in the brain.

Two experiments on the foraging tactics of rhesus macaques helped the multidisciplinary team single out one particular region that seems to rally most for behavioral change: the posterior cingulate cortex (PCC).

Housed in the upper part of the limbic lobe, the PCC has been linked to relationships between emotion and memory, including configural learning and the salience of certain life experiences in shaping our behavior.

Penn psychology professor Michael Platt and colleagues conducted the rhesus macaque experiments while recording neuron behavior in the monkeys' PCCs.

The first experiment, called the patch-leaving task, gave both lab and wild monkeys a choice between harvesting an immediate, gradually diminishing juice reward or moving on to search for a potentially more bountiful patch.

"Imagine you're picking berries in a tree," Platt said. "At first it's easy, but after a while, you have to climb farther and farther out on weaker branches to get the berries, most of which probably aren't ripe. At some point, it makes sense to take the time and energy to go to the next tree."

The second task, called the traveling salesman, gave the monkeys an option to visit six different locations, only two of which contained rewards — one large and one small. In each trial, the reward spots were randomized.

"The optimal solution is to develop a routine where you visit all of them in a circle. That's the best you can do; you go from nearest neighbor to next neighbor," Platt said. "That's what monkeys do in the wild. That's what bumblebees do in the wild. Occasionally, these animals break off to explore for something that might be better, kind of like what people do in a grocery store. Suddenly monkeys here would break off and go out of order. We didn't know why."

What the researchers noticed in the brain recordings was that neural activity built up in the PCC just before the monkeys made decisions to break their patterns. They concluded that these spikes in activity lead to divergent thinking and activity rather than the other way around.

"If you increased activity in the area exogenously, if I put an electrode in there and stimulated, then you would break off from the routine, you would become more exploratory," Platt said. "Similarly, if you could suppress activity, you'd see the opposite. You'd become hyper-focused on one option, and you may never make a change."

Techniques developed from these findings could potentially be useful in the world of business innovation and exploration, where brain stimulation and games might help break through creative ruts.

"People who have more activity there have more mind-wandering, and they tend to be more creative," Platt said. "It suggests that capacity to be more creative evolved for a very specific purpose, which is to allow you to forage efficiently in a landscape that's always changing."

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