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Two roads diverged

I'm Bob Karson with the Discovery Files, from the National Science Foundation.

One of our brain's most amazing abilities is to imagine things that aren't right in front of us. There's still no good explanation for how the brain does it: imagining possible futures in real time to help us make everyday decisions (Sound effect: car interior, horn honks, pull out) while simultaneously keeping track of reality.

In a study of rats navigating a simple maze, neuroscientists at UC San Francisco have discovered how the brain may generate imagined future scenarios.

Scientists know the brain's hippocampus contains what are called 'place-cells,' that keep track of an animal's location and travel direction (Sound effect: cartoon rat GPS voice) -- sort of a built-in GPS.

The researchers tested rats in a maze, monitoring brain activity. Every time one came to a fork, their place-cell activity began to switch back and forth at a rate of eight times a second -- between representing the animal's current position and its imagined alternatives.

The team says the regular switching between present and possible paths -- between actual and envisioned -- is not just a way for mechanically remembering or predicting. It seems to be a robust system for generating lots of ideas. The hippocampus might be at the root of our ability to imagine.

Sorta, "making this up as we go along."

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