March 28, 2024

Researchers Have Uncovered New Functions of the “Ancient Brain”

The hindbrain is a region of the brain that manages fundamental important functions such as heart rate, balance, and respiration. The hindbrain is considered the most primitive part of the brain and functions as the main link in between the spine and the higher brain regions.
A multiregional hindbrain circuit enables animals to restore their pathing after deviating from it.
A zebrafish heads toward its target, however strong currents push it off course. Undeterred, the small fish go back to its beginning point, undaunted in finishing its journey.
How do animals know where they are in their environment, and how does this identify their subsequent choices? Researchers at Howard Hughes Medical Institutes Janelia Research Campus discovered that the hindbrain– an evolutionarily saved or “ancient” region in the back of the brain– helps animals compute their location and utilize that information to determine where they require to go next.
The brand-new research, which was recently released in the journal Cell, discovers new functions for parts of the “ancient brain,” findings that could apply to other vertebrates.

This video shows whole-brain recordings of the larval zebrafish taken while it remained in the virtual reality environment. Credit: Misha Ahrens
Whole-brain imaging exposes brand-new networks
To find out how animals understand their position in the environment, scientists, led by En Yang, a postdoc in the Ahrens Lab, put small translucent zebrafish, hardly half a centimeter in length, in a virtual truth environment that replicates water currents. When the present shifts suddenly, the fish are initially pushed off course; nevertheless, they are able to correct for that movement and get back to where they began.
While a zebrafish is swimming in the virtual reality environment, the scientists use a whole-brain imaging technique developed at Janelia to measure what is occurring in the fishs brain. This method enables the scientists to browse the whole brain to see which circuits are triggered during their course-correcting behavior and disentangle the individual parts included.
The researchers anticipated to see activation in the forebrain– where the hippocampus, which includes a “cognitive map” of an animals environment, is situated. To their surprise, they saw activation in numerous regions of the medulla, where information about the animals area was being sent from a freshly recognized circuit via a hindbrain structure called the inferior olive to the motor circuits in the cerebellum that make it possible for the fish to move. When these paths were blocked, the fish was unable to browse back to its initial area.
This video shows a virtual reality environment for larval zebrafish. The fish traverses a 2D environment in the presence of a simulated water flow. Credit: Misha Ahrens
These findings recommend that areas of the brainstem keep in mind a zebrafishs initial location and generate an error signal based upon its previous and existing places. This info is communicated to the cerebellum, permitting the fish to swim back to its starting point. This research exposes a brand-new function for the inferior olive and the cerebellum, which were understood to be included in actions like reaching and locomotion, but not this kind of navigation.
” We discovered that the fish is attempting to calculate the distinction between its existing place and its chosen place and uses this distinction to produce a mistake signal,” says Yang, the very first author of the new research study. “The brain sends that error signal to its motor nerve center so the fish can fix after being moved by flow accidentally, even numerous seconds later.”
A new multiregional hindbrain circuit
It is still uncertain whether these very same networks are associated with comparable habits in other animals. But the researchers hope labs studying mammals will now begin looking at the hindbrain for homologous circuits for navigation.
This hindbrain network could also be the basis of other navigational abilities, such as when a fish swims to a specific place for shelter, state the researchers.
” This is a very unidentified circuit for this kind of navigation that we believe might underlie greater order hippocampal circuits for expedition and landmark-based navigation,” states Janelia Senior Group Leader Misha Ahrens.
Recommendation: “A brainstem integrator for self-location memory and positional homeostasis 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, 22 December 2022, Cell.DOI: 10.1016/ j.cell.2022.11.022.

The scientists expected to see activation in the forebrain– where the hippocampus, which consists of a “cognitive map” of an animals environment, is located. To their surprise, they saw activation in several areas of the medulla, where info about the animals location was being sent from a recently determined circuit by means of a hindbrain structure called the inferior olive to the motor circuits in the cerebellum that make it possible for the fish to move. When these pathways were blocked, the fish was unable to navigate back to its initial area.
The fish passes through a 2D environment in the presence of a simulated water flow. This information is communicated to the cerebellum, allowing the fish to swim back to its beginning point.