Chickadees Birds Used Barcode-Like Formatting Memory To Relocate Stash Food

Black-capped chickadees have incredible memories, recalling the locations of hundreds of bits of food to help them survive the winter.

Barcode-Like Memory Formatting

Scientists at Columbia's Zuckerman Institute have discovered how chickadees recall so many details: they memorize each food location using brain cell activity similar to a barcode.

This new information may shed light on how the brain develops memories of the experiences that comprise our lives.

This barcode-like memory formatting could be a frequent technique in animal brains, including human brains.

The birds' behavior and activity at each cache site, whether it was food storage, retrieval, or stash checks, were captured on camera. The team put a sensor in each bird's brain to record the activity of neurons in the hippocampus, a brain region critical for memory formation.

The findings demonstrate that each time a bird stashed seeds, even if it was in the same position, a distinct set of neurons fired in its hippocampus, resulting in a barcode-like pattern of activity.

The same "barcode" was shown when the morsel was retrieved as when it was cached.

The barcodes were unique to place cells, which are neurons in the hippocampus that are known to play a role in memory formation for specific locations.

While place cell activity occurred whenever the bird visited a cache site, barcodes only appeared when the bird was actually storing or retrieving a seed.

Overall, the team believes a distinct mechanism is at work when birds are creating memories of individual occurrences versus creating a mental map of an area.

"These results suggest that the barcode represents a specific episodic experience, unique in place and time in the chickadee's life," the researchers report.

Scientists have long known that these birds use the hippocampus, a brain region crucial for remembering in all vertebrates, to store cache memories. However, no one had discovered the precise neuronal activity in the hippocampus that encodes episodic memories like food-caching episodes.

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Memory Genuises

Dmitriy Aronov, Ph.D., a principal investigator at Columbia's Zuckerman Institute and an assistant professor of neuroscience at Columbia's Vagelos College of Physicians and Surgeons, describes chickadees as "memory geniuses."

The species are masters of episodic memory, which is the brain's ability to recall specific events, such as storing food under tree bark or in a knothole.

This can prove to be a matter of life or death for the chickadees, since unlike most birds that live in cold places, chickadees don't migrate during the winter.

This means their survival hinges on remembering where they hid food during the warmer months, with some making up to 5,000 of these stashes per day.

The researchers also want to know if the barcoding technique discovered in chickadees is widely used in other animals, including humans. Such research may shed light on a fundamental aspect of the human experience.

"If you think about how people define themselves, who they think they are, their sense of self, then episodic memories of particular events are central to that. That's what we're trying to understand," said postdoctoral research fellow Selmaan Chettih, Ph.D., the study's co-first author along with Emily Mackevicius, Ph.D.

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