Introducing the brain: how jellyfish learn (Introduction)

by David Turell , Friday, September 22, 2023, 18:25 (426 days ago) @ David Turell

With just a few neurons:

https://www.nature.com/articles/d41586-023-02975-x?utm_source=Nature+Briefing&utm_c...

"A tiny jellyfish has, for the first time, demonstrated a mighty cognitive capacity — the ability to learn by association. Although it has no central brain, the finger-tip-sized Caribbean box jellyfish (Tripedalia cystophora) can be trained to associate the sensation of bumping into something with a visual cue, and to use the information to avoid future collisions.

"The experiment shows a type of learning called associative learning — made famous by neurologist Ivan Pavlov’s experiments with dogs in the late-nineteenth century — in which an animal learns to associate one stimulus with another through training.

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“'The box jellyfish finding is very important because it shows that a centralized nervous system, or brain, is not necessary for associative learning,” says Pamela Lyon, a cognitive biologist at the University of Adelaide, Australia.

“'It’s super,” says Gaëlle Botton-Amiot, a neurobiologist at the University of Fribourg in Switzerland, who published a study in March1 showing that the sea anemone Nematostella vectensis is also capable of associative learning. Sea anemones and jellyfish both belong to a group of organisms known as cnidarians, and Botton-Amiot thinks that “this ability to do associative learning is present across probably the entire cnidarian tree”.

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"In the wild, T. cystophora forage for tiny crustaceans between the roots of mangroves. To mimic this environment, Bielecki’s colleagues at the University of Copenhagen placed the box jellies in cylindrical tanks that had either black and white or grey and white vertical stripes on the walls. To the jellyfish, the dark stripes looked like mangrove roots in either clear or murky water.

"In the ‘murky water’ tanks, the jellyfish bumped into the wall because their visual system couldn’t detect the grey stripes very clearly. But after a few minutes — and bumps — they learnt to adjust their behaviour, pulsing rapidly to swim away from the wall when they got too close. “It was only when they had a combination of visual stimulation and mechanical stimulation that they would actually learn something” says Bielecki.

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"To better understand the mechanisms at play, Bielecki dissected out individual rhopalia — small ‘eye-brain’ complexes in the jellyfish, each containing six rudimentary eyes plus nerve centres, called pacemakers, that control the animals’ swimming pulses.

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"Just like the living box jellies in tanks, excised rhopalia could be trained to associate an electrical ‘bump’ with the appearance of a grey bar. After five minutes of training with the grey bar and the ‘bump’, the rhopalia responded to the visual cue alone by increasing their swim-pulse frequency. This confirms that the rhopalia are “where learning happens”, says Bielecki."

Comment: it shows a small network of neurons can learn. It means to me individual neurons have enormous capacity to analyze.