Physical Memories: Neurons That Keep Track

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Mapping memory
Susanne Reichinnek/Institut de neurobiologie de la mediterrane

During a recent study,  Rosa Cossart of the Institut de Neurobiologie de la Méditerranée in Marseille, France, and her team noticed something incredible. While a mouse runs on a wheel, the brain cells keep track of where it’s been. This is the same for humans. The neurons that do so fire in a sequence. For decades, it has been believed that the pattern would file in small groups, though researchers have never gotten a clear analysis of this behavior.

When neurons fire, they flood with calcium ions. Cossart’s team painted the neurons of four mice by adding a florescent protein in order to clearly see the movement. Electrodes were implanted into the brains of the mice while they preformed normal activities like walking and standing, and the florescent proteins reveled the pattern. (see image to right)

Each cell lit up in a sequential order while the mouse ran on a treadmill, and walked. When resting, the same neurons shot in the same order as they have before, but faster. It is believed that since the neurons shoot in the same order, the mouse must be reflecting on the aforementioned experience. Though not every researcher is so sure that this is the case.  George Dragoi of Yale suggests that this neural movement is default brain activity, completely unrelated to memories.

If this activity is the movement of memories, the past hypothesis that the ‘memories’ stuck together in a group has been disproven.

“We’ve been able to image the individual building-blocks of memory,” says Cossart.

 

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