Getting eight arms round autism | Spectrum
Usually, conversations that warrant animal models of autism focus on how similar a species is to humans. But Gül Dölen sees it differently. “What if we chose the animal that is least like humans?” says Dölen, associate professor of neuroscience at Johns Hopkins University in Baltimore, Maryland. “You want to compare as different animals as possible that can solve the same problems.”
This principle led Dölen to octopuses, invertebrates with eight arms, three hearts and blue blood. However, animals have at least one thing in common with humans: They are considered to be particularly clever. “Octopuses are capable of some pretty complex cognitive tasks,” she says, solving puzzles to get food and even tricking their keepers to escape aquariums. “And yet your brain doesn’t look like ours.”
Octopuses do not have a cerebral cortex or any of the brain structures involved in human social cognition. But at the molecular level, the octopus’ nervous system has a lot in common with ours. Dölen has found evidence that the signaling molecules that underlie human social behavior perform a similar function in squid.
This evidence came from an unorthodox experiment: Dölen and her team exposed the animals to 3,4-methylenedioxymethamphetamine (MDMA), the active ingredient in the drug ecstasy. MDMA interacts with receptors for the signaling molecule serotonin and thereby increases sociability. This makes people feel particularly close and connected to others. If it had a similar effect in cuttlefish, the researchers argued, studying cuttlefish could provide insight into human social behavior and its differences in autism. Scientists could also use the animals to test drugs that are similar to MDMA that improve sociability.
Dölen and her colleagues placed four Californian two-point octopuses (Octopus bimaculoides) in water containing MDMA so that the animals can absorb the drug through their gills. Then they took the animals one by one into a basin, in which the animals could choose between two chambers: one contained an object and the other housed another octopus (which was in an additional enclosure to prevent an argument). After ingesting MDMA, the typically lonely, antisocial creatures spent more time with the other octopus than with the object. In controls, it was the other way around, the researchers reported in 2018. The MDMA-exposed squids pushed their bodies so far that they pressed their bodies against the housing with the other squid and wrapped their arms around him like in an embrace.
Dölen believes that studying octopuses could help scientists understand the molecular basis of the theory of mind, the ability to infer another creature’s way of thinking. This ability can be changed in autism.
Some observations suggest octopuses have a theory of mind, she argues. For example, the larger Pacific striped octopus hunts shrimp by secretly grasping one of its arms around the shrimp’s body and tapping its rear end. The shrimp will then jump forward where the rest of the octopus is waiting to devour it. In contrast, the octopus chases hermit crabs by jumping from behind, suggesting that shrimp can see things behind them – so it has to be sneaky – but hermit crabs are blind to their butts because of their shell.
Dölen plans to disrupt the octopus versions of autism genes and study the effects on the animals’ hunting behavior. This could suggest a role these genes play in social cognition in the context of a unique animal, which in turn could inspire new autism therapies, she says.
Quote this article: https://doi.org/10.53053/YMDC5342
