Fish ‘math’ genes may help treat human neurodevelopment diseases

The human race might have descended from apes, but researchers are turning to fish to explore secrets of the human brain. International researchers are studying fish “math” genes in an effort to treat human neurodevelopment diseases.

Researchers got to this point, they say, because fish are a good model for how human brains estimate quantities. An analysis of more than 200 publications shows that fish perceive quantities using similar parts of their brains as mammals and birds. Model systems like zebrafish are remarkably close to humans on a genetic level, which is why scientists often turn to the species to better understand learning disabilities in humans.

Scientists are still investigating the specific brain circuitry that makes number processing possible, but these findings could inevitably help treat human diseases that impair the ability to do maths.

“Fish are on par with other animals in possessing a sense of quantity,” says Giorgio Vallortigara, corresponding author and professor at the University of Trento in Italy, in a statement. “These are species, most notably the zebrafish, that are ideal models for studying the molecular and genetic bases of the sense of quantity. This could have important implications for neurodevelopment diseases affecting number cognition, such as developmental dyscalculia, which impairs maths skills in up to six percent of children.”

Researchers first analyzed behavioral studies showing that fish rival mammals and birds in recognizing the difference between smaller and larger quantities. They used brain imaging to look at the cellular and genetic level to better understand how fish gauge quantity. Fish were found use the equivalent parts of their brains as many other vertebrates.

“Another open issue is whether numerical quantities are really computed as an abstract property or whether animals always think about numbers on the basis of other cues from their surroundings (such as surface area, contour length, or density),” explains Vallortigara. “However, experiments are described in this review that show that pure numerousness is indeed used by fish.”

Separate studies have gotten closer to finding the specific neurons that form the circuits that process quantity. There’s also genetic analyses that show how similar these strategies are between different species.

“A big ongoing question is whether the mechanisms for quantity cognition in the different parts of the animal kingdom evolved from a common ancestor or separately as a result of convergent evolution under similar selective pressures,” says Vallortigara.

The video shows experiments described in the lab of Prof Vallortigara and reported in Messina et al (2022). On the left side an example is shown of the procedure of habituation of a zebrafish to a certain numerosity; on the right side one can notice that during the dishabituation test when the numerosity is abruptly changed the zebrafish exhibit increased stay close to the stimulus to explore the novelty. Controls showed that zebrafish responded to numerosity as such and not just to change in area or spatial positions of the dots. (Credit: Giorgio Vallortigara / University of Trento)

The study is published in the journal Frontiers in Neuroanatomy.

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