Brain cells activated, reactivated in learning and memory

Memories are made of this, the song says. Now neuroscientists have for the first time shown individual mouse brain cells being switched on during learning and later reactivated during memory recall. The results are published Dec. 13 in the journal Current Biology.

We store episodic memories about events in our lives in a part of a brain called the hippocampus, said Brian Wiltgen, now an assistant professor at the Center for Neuroscience and Department of Psychology at the University of California, Davis. (Most of the work was conducted while Wiltgen was working at the University of Virginia.) In animals, the hippocampus is important for navigation and storing memories about places.

"The exciting part is that we are now in a position to answer a fundamental question about memory," Wiltgen said. "It’s been assumed for a long time that the hippocampus is essential for memory because it drives reactivation of neurons (nerve cells) in the cortex. The reason you can remember an event from your life is because the hippocampus is able to recreate the pattern of cortical activity that was there at the time."

According to this model, patients with damage to the hippocampus lose their memories because they can’t recreate the activity in the cortex from when the memory was made. Wiltgen’s mouse experiment makes it possible to test this model for the first time.