( Time is the most popular noun in the ...)How does your brain tell time?

For decades, scientists have believed that the brain possesses an internal clock that allows it to keep track of time. Now a UCLA study in the Feb. 1 edition of Neuron proposes a new model in which a series of physical changes to the brain’s cells helps the organ to monitor the passage of time.

"The value of this research lies in understanding how the brain works," said Dean Buonomano, associate professor of neurobiology and psychiatry at the David Geffen School of Medicine at UCLA and a member of the university’s Brain Research Institute. "Many complex human behaviors -- from understanding speech to playing catch to performing music -- rely on the brain’s ability to accurately tell time. Yet no one knows how the brain does it."

The most popular theory assumes that a clock-like mechanism ?which generates and counts regular fixed movements -- underlies timing in the brain. In contrast, Buonomano suggests a physical model that operates without using a clock. He offers an analogy to explain how it works.

"If you toss a pebble into a lake," he explained, "the ripples of water produced by the pebble’s impact act like a signature of the pebble’s entry time. The farther the ripples travel the more time has passed.

"We propose that a similar process takes place in the brain that allows it to track time," he added. "Every time the brain processes a sensory event, such as a sound or flash of light, it triggers a cascade of reactions between brain cells and their connections. Each reaction leaves a signature that enables the brain-cell network to encode time."

The UCLA team used a computer model to test this theory. By simulating a network of interconnected brain cells in which each connection changed over time in respo
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Source:University of California - Los Angeles