Marking the Birth of Memory

April 17, 2014

Neuroscientists at Johns Hopkins believe they can mark the birth of a memory in an animal by tracking its brain activity when it stops to scan its surroundings. 

Using rats on a circular track, James Knierim, professor of neuroscience in the Zanyyl Krieger Mind/Brain Institute at Johns Hopkins, and a team of scientists watched as the rodents would frequently pause to check their surroundings with swiveling head movements as they ran. This activated place cells-cells in the brain used to construct a cognitive map-creating a pattern of activity in the brain reflective of the rat’s internal representation of its environment.

"We found that many cells that were previously silent would suddenly start firing during a specific head-scanning event," Knierim said.

“We found that many cells that were previously silent would suddenly start firing during a specific head-scanning event,” Knierim said.

Found in the hippocampus (the part of the brain that processes long and short-term memory and spatial navigation), place cells are a type of neuron that activates when an animal enters a particular place in its environment. This creates a spatial framework that allows the experience to imprint itself as a memory.

“This is like seeing the brain form memory traces in real time,” said Knierim. “Seeing for the first time the brain creating a spatial firing field tied to a specific behavioral experience suggests that the map can be updated rapidly and robustly to lay down a memory of that experience.”

To track the rats’ brain activity, the researchers placed tiny wires in their brains to monitor the rats as they ran around the track looking for chocolate rewards. Hungrily scanning the track, the place cells started firing as the rats marked landmarks along the way.

“There are strong indications that humans and rats share the same spatial mapping functions of the hippocampus, and that these maps are intimately related to how we organize and store our memories of prior life events,” Knierim said. “Since the hippocampus and surrounding brain areas are the first parts of the brain affected in Alzheimer’s, we think that these studies may lend some insight into the severe memory loss that characterizes the early stages of this disease.”



Alec Schwartz
Biochemistry and Molecular Biology Major
Dickinson College
Class of 2016



Joseph D. Monaco, Geeta Rao, Eric D. Roth and James J. Knierim. (30 March 2014). Attentive scanning behavior drives one-trial potentiation of hippocampal place fields. Nature Neuroscience. doi:10.1038/nn.3687

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