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How the cuttlefish’s robust memory system defies old age

Do you remember what did you eat last weekend? This ability is a function of episodic memory, and the way we can remember the time and place of specific events generally decreases with age. Cuttlefish also appear to exhibit some form of episodic memory, but unlike humans, their ability does not decrease with age, according to a new paper published in the Proceedings of the Royal Society B.

“Cuttlefish can remember what they ate, where and when, and use it to guide their feeding decisions in the future,” said co-author Alexandra Schnell of the University of Cambridge, who conducted the experiments at the Marine Biological Laboratory in Woods Hole, Massachusetts. “What is surprising is that they don’t lose this ability with age, despite other signs of aging such as loss of muscle function and appetite.”

Earlier this year, we reported on a study by Schnell and other colleagues showing that cuttlefish can delay gratification. Specifically, they could pass a cephalopod version of the famous Stanford Marshmallow Test: wait a little for your favorite prey rather than settling for less desirable prey. The cuttlefish also performed better in a subsequent learning test – the first time such a link between self-control and intelligence has been found in a non-mammalian species.

In these experiments, the cuttlefish had to choose between two different prey: it could choose to eat the raw king shrimp immediately or delay the gratification of the preferred green shrimp. The subject could see both options for the duration of the trial and could forgo waiting at any time and eat the king shrimp if he was fed up with waiting for the green shrimp.

The team also subjected the cuttlefish to a learning task to assess cognitive performance. Cephalopods first learned to associate a visual symbol with a specific prey reward, and then the researchers reversed the situation so that the same reward was associated with a different symbol. They found that cuttlefish were all able to wait for the best reward and tolerated delays of up to 50 to 130 seconds, comparable to large-brained vertebrates such as chimpanzees, crows, and parrots.

This latest study focuses on whether cuttlefish have some form of episodic memory – the ability to remember unique past events with the context of what happened, where it happened and when it happened. arrived. Humans develop this ability around the age of 4, and our episodic memory declines as we move into old age. This contrasts with semantic memory, our ability to recall general knowledge learned without the context of space and time. Semantic learning in humans has been shown to remain relatively intact with age.

The hippocampus region of the human brain plays an important role in episodic memory, and its deterioration over time is believed to be responsible for the decline in our episodic memory as we age. For a long time, scientists assumed that episodic memory was uniquely human, because this type of memory retrieval is associated with the conscious experience of remembering. Humans can express these aspects verbally; it is much more difficult to assess the possible conscious experience in nonverbal animals (in human terms).

Nonetheless, several animal species have been shown to exhibit “episodic-type” memory capacities – the term scientists in this subfield use for “explicitly recognize that we do not assume the human attributes of language and speech. consciousness involved in the consciousness of self-projection in time ”, as Schnell et al. written in a footnote. For example, a 1998 study discovered that jays can remember when and where they stored stuffed food and what the food was. Behaviors indicative of episodic memory have also been observed in magpies, the great apes, rats, and zebra fish.

Evidence of episodic-type memory has also been found in cuttlefish. Cuttlefish do not have a hippocampus, but they do have a distinctive brain structure and organization, with a vertical lobe that bears similarities to the connectivity and function of the human hippocampus, i.e. the learning and memory. Previous studies have shown that cuttlefish are sufficiently forward-looking and can optimize foraging behavior and remember details of what, where and when past forages – characteristic of episodic memory – by adjusting their strategy. in response to changing prey conditions.

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