The Amygdala's Role in Memory Formation: What New Research Reveals

Historically, the hippocampus has been regarded as the central structure for the formation of memories. But new Cedars-Sinai research suggests the amygdala may play an earlier and more active role in memory formation.  

The results could guide development of treatments for memory disorders such as Alzheimer’s disease.

“Every day, we encounter lots of stimuli—the food we eat, the people we meet, the sights we see—but we retain only a small number of them in our memory,” said Jiayang Xiao, PhD, the study’s lead author and a postdoctoral fellow in the Rutishauser Laboratory at Cedars-Sinai. “We wanted to understand what makes a memory stick.”

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Patients with brain-implanted electrodes for epilepsy treatment provided researchers a chance to record single-neuron data from the amygdala, hippocampus and other brain regions. Investigators showed the subjects novel images chosen from five categories: faces, animals, food, cars and landscapes. After 10-15 minutes, they re-presented some of the same images as well as new ones, asking the subjects which pictures they remembered seeing before.

We could predict which images would be remembered and which would be forgotten.

The results showed neurons in the amygdala, primarily in the right hemisphere, were more strongly associated with successful memory formation than those in the hippocampus. Interestingly, each amygdala neuron only fired, or fired most strongly, in response to a specific preferred image category and predicted the success of memory formation only for images from that category.  

“Based on the strength of the neural responses in the amygdala to the novel images, we could predict which images would later be remembered and which would be forgotten,” Xiao said.  

Investigators also looked at local field potentials—the combined activity of many neurons. They found that coordination between brain regions is likely enhanced during more successful memory formation.

“The study’s results suggest that activating category-selective neurons in the amygdala triggers memory formation,” Xiao said. “If so, stimulating these neurons in the amygdala specifically might be a novel treatment for memory disorders.”