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Despite what you may think, your brain is a mathematical genius

Sergei Gepshtein and Thomas D. Albright

From left: Sergei Gepshtein and Thomas D. Albright

After hours of dodging dangerous drivers, you finally arrive at a quiet mountain retreat, gaze at a pristine lake and congratulate yourself for having "turned off your brain."

But actually, according to Thomas D. Albright, an expert on how the visual system works, you've just given your brain a whole new challenge. "You may think you're resting," he says, "but your brain is automatically assessing the spatiotemporal properties of this novel environment—what objects are in it, are they moving, and if so, how fast are they moving?"

The dilemma is that our brains can only dedicate so many neurons to this assessment. "It's a problem in economy of resources," says Sergei Gepshtein, a computational neuroscientist and staff scientist in Albright's lab. "If the visual system has limited resources, how can it use them most efficiently?"

Albright, Gepshtein and Luis A. Lesmes, a specialist in measuring human performance and former Salk postdoctoral researcher now at the Schepens Eye Research Institute, proposed an answer in a study published in Proceedings of the National Academy of Sciences that may reconcile the puzzling contradictions in many earlier studies.

Previously, scientists expected that extended exposure to a novel environment would make you better at detecting its subtle details, such as the slow motion of waves on that lake. Yet those who tried to confirm that idea were surprised when their experiments produced contradictory results. "Sometimes people got better at detecting a stimulus, sometimes they got worse, sometimes there was no effect at all, and sometimes people got better, but not for the expected stimulus," says Albright.

The answer came from asking a new question: What happens when you look at the problem of resource allocation from a system's perspective? It turns out that something's got to give, and the team's study details the computations the visual system uses to accomplish the adaptation.

"It's as if the brain's on a budget; if it devotes 70 percent here, then it can only devote 30 percent there," says Gepshtein.

"Simply put, it's a tradeoff," Albright adds. "The price of getting better at one thing is getting worse at another."