When video game players are robbing a bank or strolling the crime-ridden streets of downtown Miami while playing “Grand Theft Auto,” they are focusing on the police in their way and the firearms in their hands, not the birds in the sky or the billboards on the skyline. This is a prime example of how visual information is trimmed away before being examined by the brain, researchers at Yale are beginning to uncover.
A team of Yale scientists led by School of Medicine neurobiology professor David McCormick found that certain brain cells save the brain energy by pruning information gathered by the five senses. McCormick said he hopes the team’s findings could change how medical professionals treat eye disorders.
McCormick said he sought to find how the brain handles sensory information efficiently. Previous studies had shown that the brain uses the highest relative percentage of the body’s total energy as much as one-fifth of the energy derived from food, he said. Most research had used a limited number of simple stimuli, such as bright and dark bars, to test how the brain processes information, but McCormick’s study introduced more stimuli.
“A lot of studies use very simple stimuli to keep things under control,” McCormick said.
The team’s study on animal test subjects employed videos of nature scenes to test how their brains processed stimuli. McCormick’s team installed electrodes that were the less than the width of a human hair into brain cells. The electrodes are able to monitor what signals the brain cells are receiving and sending out, he said.
The results were surprising, McCormick said. His team found that the brain works much like an MP3 file, which takes a complex concert of notes and rhythms and compresses them down into a small, manageable file. In the brain, inhibitory brain cells save energy by disregarding “non-essential stimuli,” such as background noise and objects in peripheral vision.
“What really captures your attention is what’s straight ahead,” McCormick said.
McCormick called this the “iceberg phenomenon.” Just as one-seventh to one-tenth of an iceberg glides above the water’s surface, McCormick said, only a fraction of visual input dominates the visual cortex.
McCormick’s team, which included Yale researchers Bilal Haider and James Mazer, published their results in the journal Neuron on Jan. 14. Their work was funded by the National Eye Institute and the Kavli Foundation, which funds science research.