Eureka, brain makes real mental leaps

Rat studies reveal pattern of neuron firing shifts during aha moments

Sometimes when a reporter is thinking about how to start a story, she has one of those aha moments, and clever words are typed.

This is not one of those times. But if it had been, a new study could offer some insight into what happened when that elusive moment of inspiration did occur.

An aha moment comes when neurons in the brain alter their activity all at once, scientists report in the May 13 Neuron. The study is evidence that brain cells act in concert during moments of insight, says study coauthor Daniel Durstewitz, a computational neuroscientist at the University of Heidelberg in Germany.

The findings are evidence that the standard model of learning — in which some brain connections strengthen with repeated use and others wither with lack of exercise — doesn’t always apply, says Randy Gallistel, codirector of Rutgers University’s Center for Cognitive Science in New Brunswick, N.J, who was not part of the new study.

To locate an aha in the brain, Durstewitz and his colleague Jeremy Seamans at the University of British Columbia in Canada, tracked activity in the prefrontal cortexes of rats that were learning new tasks. The prefrontal cortex is known to be involved in executive decision making, planning ahead and adjusting to new situations.

The researchers designed an experiment that required the rats to learn that the rules for a task had changed, the kind of challenge that might lead to an aha.

“So you not only have to learn something new, but you have to let go of something else,” says Durstewitz. “You have to inhibit yourself.”

First, the researchers trained 13 rats on a simple visual task. They presented the rats with two levers, each with a light above it. When a light blinked on, the rat had to hit the lever below it to get a food pellet.

After the rats had mastered the task, the scientists switched things up. The task became spatial: No matter which light turned on, one lever only — the left or the right, depending on the rat — brought the food reward.

When each rodent figured out the new system, its aha moment could be seen as a change in brain activity. Electrodes implanted in the rats’ prefrontal cortexes recorded a sudden across-the-board change in the pattern of firing neurons; dimly firing cells amped up, while previously hyper cells calmed down.

About half the rats learned the new rule quickly, accompanied by the sudden switch in neuron activity. Other rats seemed to realize the old rule wasn’t working, but hadn’t quite figured out the new rule. In their brains, some neurons began to change their firing intensity, then a few more, and then, bam, the rats understood the new rule and the new firing pattern took hold.

Whether the change in brain activity causes the insight, or the other way around, is not clear, the researchers say. Sometimes rats appeared to get the new task right slightly before the shift in neuron activity. Perhaps as the rat is starting to learn the new rules, information gradually builds up in one part of the brain and then is suddenly transmitted to these aha neurons, the team speculates.

The researchers had an aha moment themselves during the study, Durstewitz says. While looking at their data on a computer screen, the shape of the plotted points started to look as though the rats were having a sudden revelation about the new task. “We said ‘Oh, this looks like sudden insight,’ as a joke,” Durstewitz says. “Then we thought, wait — this is going on — this is sudden insight!”

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