While adults may spend the weekend trying to remember where they hid a treasure of Easter eggs, the black-capped chick has no trouble remembering where its treats are stashed. Now researchers have discovered why: the tiny birds create a barcode-like memory every time they store food.
Black-headed chicks are known to hide food in the warmer months – with some estimates suggesting that a single bird can hide up to 500,000 food items per year. But even more remarkable is their reliability in finding the pieces again.
Now researchers say they have unpicked the mechanism behind the feat. Write in the journal Cell scientists in the US report how they gave chicks sporadic access to sunflower seeds within an arena with more than 120 places where food could be stored.
The behavior of the birds and the activity at each cache site – be it storing food, retrieving food or checking on a stash – was recorded on video.
The team used an implanted probe in the brain of each bird to record the activity of neurons in its hippocampus – a brain structure essential for memory formation.
The results show that every time a bird stored seeds, even if they were in the same place, a different combination of neurons in its hippocampus fired, resulting in a barcode-like pattern of activity.
The same “bar code” was observed when the piece was located as it was when it was stored in the cache.
The barcodes were distinct from place cells – neurons in the hippocampus known to be involved in forming memories involving specific locations. “The two randomly overlapped so that neurons could not be one, one or both,” said Dr. Selmaan Chettih of Columbia University, first author of the study.
Indeed, while location activity occurred every time the bird visited a cache location, the barcoding only occurred when the bird was actually storing or retrieving a seed. Overall, the team suggests that a different mechanism is at work when the birds make memories of specific events, as opposed to when they make a mental map of an area.
“These results suggest that the barcode represents a specific episodic experience, unique in place and time in the chick’s life,” the researchers report.
Chettih added that although it had not yet been proven, it was possible that the findings also applied to human and other mammalian brains. “The message is that, when you form a memory of a particular event, your brain can generate a random label that it uses to store information associated with that event in a way analogous to the way on which a store records information that must be retrieved with each product when the label is scanned,” he said. “Perhaps another message is that the brains and mental capacities of these small, common birds can be quite remarkable.”
