‘Mathematical’ genes used by fish to count could help us treat human neurodevelopmental diseases

Fish are helping researchers trace the origins of how brains compute math, reports a review in Frontiers in Neuroanatomy. An international team reviewed more than 200 publications, which together show that fish perceive quantities using parts of their brains similar to those used by mammals and birds. Research is still ongoing to find the specific brain circuitry that makes number crunching possible, but these findings could eventually help treat human diseases that impair the ability to do math.

“Fish are on par with other animals in possessing a sense of quantity,” said corresponding author Prof. Giorgio Vallortigara from the University of Trento, Italy. “There are species, particularly zebrafish, that are ideal models for studying the molecular and genetic basis of quantity sense. This could have important implications for neurodevelopmental diseases that affect numerical cognition, such as developmental dyscalculia, which impairs math skills in up to 6% of children.”

fish lessons

Estimating quantity is essential for a fish’s survival. Vallortigara and his collaborators started with a collection of behavioral studies showing that fish rival mammals and birds in recognizing the difference between larger and smaller amounts — of food or other fish, for example.

Many investigations have also used behavior to try to understand how fish measure quantity, but Vallortigara’s team found that this required a closer look at the cellular and genetic level. To answer these questions, the researchers used brain imaging to show that fish use the same parts of their brains as many other vertebrates.

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

The evolution of mathematics

On an even more detailed level, other studies have come closer to finding the specific neurons that form the circuits that process quantities, including those specific to discrete quantities. Genetic analyzes are also revealing exactly how similar these strategies are across different species.

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

On a genetic level, model systems like zebrafish are surprisingly close to humans, and many researchers have used zebrafish to better understand learning disabilities in humans.