Scientists at the BioRobotics Lab in EPFL and Duke University studied how larval zebrafish navigate using their brains and bodies together. Unlike typical lab studies that focus only on the brain, this research looked at how the environment, like water currents, shapes fish behavior. Larval zebrafish are tiny, transparent fish whose neurons can be seen clearly, making them ideal for studying brain activity. The goal was to understand how the body affects how the brain processes information from the environment.
The study, published in Science Robotics, used a computer simulation to mimic a zebrafish’s brain, body, and environment. The simulation copied the fish’s neural network of connected neurons based on real-time brain imaging from live fish. It included the retina (the part of the eye that detects light) and spinal cord to show how the fish processes visual information and moves. The simulation focused on the optomotor response, a reflex where fish swim to stay in place against water currents. The virtual fish behaved like real fish, showing the same swimming patterns when shown visual stimuli (images or patterns) that mimicked flowing water. The simulation also revealed two new types of neurons that help explain how fish react to unusual sights.
Real-world testing with a robotic fish
To test the simulation in the real world, researchers built an 80-cm robotic zebrafish with cameras for eyes and motors to move its tail. The robot used the same neural circuits as the simulation. In tests in Lausanne’s Chamberonne River, the robot could stay in place against the current, proving the neural circuits worked in a natural, unpredictable environment. This showed that vision alone could be enough for zebrafish to navigate, a significant finding since animal behavior often includes random responses.
The simulation and robot designs are open-source, so that other scientists can use them to study animal behavior. This work highlights how simulations and robots can show which brain mechanisms are enough for specific behaviors, offering new ways to understand how brains and bodies interact in nature.