Simulated sea slug gets addicted to drug

Date:
June 16, 2020
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
Scientists built a computer model of a simple brain network
based on that of a sea slug, taught it how to get food, gave it
an appetite and the ability to experience reward, added a dash of
something called homeostatic plasticity and then exposed it to a
very intoxicating drug.

To no one's surprise, the creature became addicted.



FULL STORY ========================================================================== Scientists built a computer model of a simple brain network based on that
of a sea slug, taught it how to get food, gave it an appetite and the
ability to experience reward, added a dash of something called homeostatic plasticity and then exposed it to a very intoxicating drug. To no one's surprise, the creature became addicted.


==========================================================================
The research is part of a long-term project to create a working model
of the brain, starting with the simplest of circuits and gradually
adding complexity, said Rhanor Gillette, a University of Illinois
at Urbana-Champaign professor emeritus of molecular and integrative
physiology who led the research.

Postdoctoral researcher and lead author Ekaterina Gribkova built the
computer model based on previous work by co-author Marianne Catanho,
now at the University of California, San Diego. They describe their work
in the journal Scientific Reports.

"By watching how this brain makes sense of its environment, we expect to
learn more about how real-world brains work," Gillette said. "We also
think our model will make a great educational tool." The researchers
named their model slug ASIMOV after the well-known science fiction
writer Isaac Asimov, who was among the first to think and write about
the ethics of robotics. They set the creature loose in a confined area
where it would randomly encounter pellets of food, some of which were delicious, others noxious.

Just like a real predator, ASIMOV learned to avoid the noxious prey items
and gobble up the good ones -- unless it was very hungry, in which case
it would eat whatever crossed its path. Each type of pellet had its own characteristic odor that enabled ASIMOV to determine whether to turn
toward it in pursuit or to avoid it.

In addition to eating to become satiated, ASIMOV was also able to
experience reward. Maximizing its own satiation levels and reward
experiences were the creature's two life goals.



========================================================================== After establishing that ASIMOV could discriminate between good and bad
foods, the researchers then added a highly rewarding but nutritionally
empty drug pellet to their model. The drug also had its own characteristic odor. Once ASIMOV consumed it and experienced the intoxicating reward,
it began to pursue the drug to the exclusion of all else.

The drug also made ASIMOV feel satiated, satisfying both life goals. But
these two "mental" states were temporary. Eating caused satiation,
but that feeling of fullness waned over time. Furthermore, ASIMOV was
designed to habituate to the drug, Gribkova said.

"Just like when you drink coffee every day, you get used to the effects,
which lessen over time," she said. "And if you stop drinking coffee,
you go into withdrawal." This was the homeostatic plasticity feature
kicking in, Gillette said. "ASIMOV started going into withdrawal, which
made it seek out the drug again as fast as it could because the periods
during which a reward experience last were getting shorter and shorter," Gillette said.

Then the researchers took the drug away from ASIMOV. The creature
experienced full-fledged withdrawal and, eventually, became resensitized
to the drug.



========================================================================== ASIMOV's behavior followed the course of addiction seen in other
organisms, including humans, the researchers said. Guided by desire for
reward and satiation, but also attempting to avoid pain, the creature
cycled between eating, not eating and chasing after the drug when it
was available.

"If it's very intoxicated by the drug, what usually happens in our
simulation is that it just ignores all the other options -- for example,
the option to eat," Gribkova said. "It ends up in this malnourished and intoxicated state.

But if it goes into withdrawal because it can't find the drug, it loses
its selectivity for different kinds of prey. It just eats everything
in sight.

"We wanted to actually recreate addiction in this organism," she
said. "And this is the simplest way we could do it." "We expect that behavioral complexity in animals probably evolved from very simple
beginnings like this, so we're trying to recreate that in a very
evolutionarily plausible way," Gillette said.

The researchers say they aim to add more layers of complexity in future
work, tackling attributes like social behavior and altruism.

The National Institutes of Health and National Science Foundation
supported this research.


========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Diana Yates. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Ekaterina D. Gribkova, Marianne Catanho, Rhanor Gillette. Simple
Aesthetic Sense and Addiction Emerge in Neural Relations of
Cost-Benefit Decision in Foraging. Scientific Reports, 2020; 10
(1) DOI: 10.1038/ s41598-020-66465-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200616113903.htm

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