Can you remember what you had for dinner last weekend? This ability is called episodic memory. As we age, our recall of the times and places of particular events decreases. According to new research published in the Proceedings of the Royal Society, Cuttlefish may also exhibit episodic memory. However, unlike humans, this ability doesn’t diminish with age.
Alexandra Schnell, coauthor of the University of Cambridge and who carried out the experiment at Woods Hole’s Marine Biological Laboratory, Massachusetts, said that cuttlefish are able to remember where they ate and how long ago. It’s amazing that this ability doesn’t diminish with age, even though they show other signs such as loss of appetite and muscle function.
We reported earlier this year on Schnell’s and others’ study that showed cuttlefish could delay gratification. Specifically, they could pass a cephalopod version of the famous Stanford marshmallow test: waiting a bit for their preferred prey rather than settling for a less desirable prey. A subsequent learning test showed that Cuttlefish performed well, marking the first instance of a connection between intelligence and self-control in non-mammalian animals.
The cuttlefish was given two options for prey: it could choose either to immediately eat raw kingprawn or wait to get its preferred live grass shrimp. The cuttlefish could view both the options and was able to choose whether it wanted the grass shrimp or the raw king prawn.
To assess the cognitive abilities of cuttlefish, the team put them through a learning task. Researchers reversed the process so the reward associated with the exact prey reward could be seen by the cephalopods. The researchers found that cuttlefish could wait up to 50-130 seconds for the best reward, which is comparable to larger-sized vertebrates like chimpanzees and crows.
The latest research focuses on cuttlefish’s episodic memory. This is the ability to remember unique past events and provide context. It also includes information about where they happened, when it occurred, and what it was. This ability is developed in humans around the age of 4, but our episodic memories decline as we age. This contrasts with semantic memory which is our ability to remember general knowledge in a context that doesn’t include time and space. It has been demonstrated that semantic learning remains relatively stable as we age.
Human brain’s hippocampus plays an essential role in episodic memories. It is believed that as we age, our episodic memory declines because of this deterioration. Scientists believed that episodic memories were unique to humans because it is linked with conscious experiences of recall. These aspects can be expressed verbally by humans; however, it is much harder to assess the conscious experience of nonverbal animals (in human terms).
However, many animal species are capable of “episodic like” memory abilities. This term is used by scientists in the subfield to “explicitly admit that we don’t assume human attributes such as language or consciousness in the awareness of oneself in time.” Schnell et. al. In a footnote, Schnell et al. For instance, a 1998 study found that jay birds can remember when and where they stored foraged food and what the food was. Magpies, rats, great apes and zebrafish also display episodic-like memories.
Evidence of episodic-like memory has also been shown in cuttlefish. Although cuttlefish do not have a hippocampus they possess a brain structure similar to that of humans. This includes a vertical-lobe brain structure. It also functions similarly to the human hippocampus in terms of learning and memory. Studies in the past have demonstrated that cuttlefish can be future-oriented, optimize their foraging behaviors, remember specific details from previous forages, as well as adjust their strategies to adapt to changes in prey conditions.
However, does this ability change with age? Schnell and colleagues. To answer this question, Schnell et al. developed cuttlefish memory tests that were both episodic and semantic. Cuttlefish have a two-year life expectancy, making them an ideal candidate for such research.
Schnell and her coworkers used 24 common cuttlefish for their experiments. Half of them were younger (10-12 months) and half were older (22-24 months), which is roughly the age of an adult human. They were all raised from eggs obtained at the Marine Biological Laboratory. Each fish was kept in its own tanks. First, the team trained cuttlefish to recognize visual cues by placing flags in specific areas of their tanks.
Similar to Schnell’s previous work regarding delayed gratification the cuttlefish were able to choose which prey they preferred. In this instance, it was either live grass shrimp or equal-sized prawn meat. The cuttlefish learned that the two kinds of prey they wanted were only available in specific places (marked with the waving flags). These locations were marked by the wave of the flags. To ensure the cuttlefish didn’t just learn a pattern, each of these two feeding spots was unique.
Schnell et.al. Surprisingly, Schnell et al. This is the first time that an animal doesn’t show age-related decline in recalling events. This remarkable strength is likely due to the fact that the cuttlefish’s vertical lobe doesn’t change until after they stop eating.
According to the authors, this may be a result of evolutionary pressures. This is especially true since cuttlefish are more likely to mate later in life. Schnell stated that the old cuttlefish performed just as well as the younger fish in memory tasks. In fact, the test phase showed that many older cuttlefish did better. This ability may help wild cuttlefish remember their mate so that they do not re-match with the same person.
Cuttlefish can still experience memory loss as they age. The authors referenced several studies that showed lower memory retention scores in older cuttlefish, which could be a sign of age-related memory loss.
The authors think it will be beneficial to study the neuroanatomy and behavior of cuttlefishes in the future. Researchers would like to know when cuttlefish develop episodic memory, whether it is shortly after hatching or later.
The authors conclude that “Overall these findings highlight common cuttlefish to be an interesting model for studying resistance to age-related declines in episodic-like memories system.”
Original publication: Ars Technica.
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Publiated at Sun, 22 August 2021 13:03.50 +0000