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Anyone who has ever been in an earthquake has vivid memories of it: the ground shakes, trembles, buckles and heaves; the air fills with sounds of rumbling, cracking and shattering glass; cabinets fly open; books, dishes and knickknacks tumble from shelves. We remember such episodes—with striking clarity and for years afterward—because that is what our brains evolved to do: extract information from salient events and use that knowledge to guide our responses to similar situations in the future. This ability to learn from past experience allows all animals to adapt to a world that is complex and ever changing.

For decades, neuroscientists have attempted to unravel how the brain makes memories. Now, by combining a set of novel experiments with powerful mathematical analyses and an ability to record simultaneously the activity of more than 200 neurons in awake mice, my colleagues and I have discovered what we believe is the basic mechanism the brain uses to draw vital information from experiences and turn that information into memories. Our results add to a growing body of work indicating that a linear flow of signals from one neuron to another is not enough to explain how the brain represents perceptions and memories. Rather the coordinated activity of large populations of neurons is needed.

   
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