The hindbrain is the part of the brain that controls fundamental functions such as heart rate, breathing and balance. The hindbrain is the most primitive part of the brain and serves as the main link between the spinal cord and the higher brain.
Several regions of the hindbrain circuit enable animals to reverse course after deviating from it.
Zebra fish head towards the target. But the strong current pushed it off course. The small fish returned undeterred to their starting point. determined to end the journey
How do animals know where they are in the environment? And how does this determine their subsequent choice? Researchers at the Howard Hughes Medical Institute’s Janelia Research Campus discovered that the dorsal brain, the evolutionarily conserved “ancient” part of the brain, lies at the back. of the brain Help animals calculate their location and use that information to figure out where to go next.
New research just published in the journal cellIt reveals new functions for different parts of the “ancient brain,” a discovery that may apply to other areas.[{” attribute=””>vertebrates.
This video shows whole-brain recordings of the larval zebrafish taken while it was in the virtual reality environment. Credit: Misha Ahrens
Whole-brain imaging reveals new networks
To figure out how animals understand their position in the environment, researchers, led by En Yang, a postdoc in the Ahrens Lab, put tiny translucent zebrafish, barely half a centimeter in length, in a virtual reality environment that simulates water currents. When the current shifts unexpectedly, the fish are initially pushed off course; however, they are able to correct for that movement and get back to where they started.
While a zebrafish is swimming in the virtual reality environment, the researchers use a whole-brain imaging technique developed at Janelia to measure what is happening in the fish’s brain. This technique allows the scientists to search the entire brain to see which circuits are activated during their course-correcting behavior and disentangle the individual components involved.
The researchers expected to see activation in the forebrain – where the hippocampus, which contains a “cognitive map” of an animal’s environment, is located. To their surprise, they saw activation in several regions of the medulla, where information about the animal’s location was being transmitted from a newly identified circuit via a hindbrain structure called the inferior olive to the motor circuits in the cerebellum that enable the fish to move. When these pathways were blocked, the fish was unable to navigate back to its original location.
This video shows a virtual environment for zebrafish larvae. Fish move through a 2D environment with simulated water flow. Credit: Misha Ahrens.
These findings suggest that parts of the brainstem remember their original location in zebrafish. and generate error signals based on its current and past positions. This information is then passed on to the cerebellum. allowing the fish to swim back to the starting point This research reveals a new function for the inferior olive and cerebellum. This is known to involve actions such as reaching and moving. But not this type of navigation.
“We found that the fish were trying to calculate the difference between their current position and their intended position. and use this difference to generate false signals,” said Yang, the first author of the new study. “The brain sends that error signal to its motor control center. so that the fish can fix it after being accidentally carried away by the current. Even if several seconds have passed.”
New multiregional hindbrain circuits
It is not clear whether these same networks are involved in similar behavior in other animals. But researchers hope that laboratories studying mammals will start looking in the hindbrain for similar circuits for navigation.
This hindbrain network can also be the basis for other navigational skills, such as when a fish swims to a specific cover. researchers say
“This is a very unknown circuit for this type of navigation. which we think may support higher-order hippocampal circuits for observation and landmark-based navigation,” said Misha Ahrens, senior group leader, Janelia.
Reference: “Brainstem Integrators for Self-Location Memory and Locatiotility in Zebrafish” by En Yang, Maarten F. Zwart, Ben James, Mikail Rubinov, Ziqiang Wei, Sujatha Narayan, Nikita Vladimirov, Brett D. Mensh, James E. Fitzgerald and Misha B. Ahrens December 22, 2022 cell.
doi: 10.1016/j.cell.2022.11.022
