This part of the brain might perform a similar function in other vertebrates, including humans
Photo: iStock_ Fish that have lost their way rely on an ancient part of the brain to understand their current location and swim back to safety, according to a new study.
The ancient part of the brain, the inferior olive, is evolutionarily conserved, the study published in the biology journal Cell reported. This means it has remained the same over years of evolution.
“Our results support the idea that evolutionarily ancient brain regions contribute centrally to higher-order behaviours,” the study read.
These findings suggest that this part of the brain might perform a similar function in other vertebrates.
Humans, too, possess inferior olivary nuclei — a part of the brainstem that sits above the spinal cord. It is thought to be involved in the development of fine motor control and coordination.
Many animals keep track of their location in their environment. This helps them efficiently return to safe places after visiting unknown and potentially dangerous areas, revisiting food-rich areas and avoiding foraging in food-poor regions, the researchers wrote in their study.
The team studied tiny translucent zebrafish, barely half a centimetre in length. They were put in a virtual reality environment that simulated water currents.
When the current shifts unexpectedly, the fish end up losing their way. These organisms, however, always found their way back.
The researchers imaged the whole brain to observe which regions of the brain lit up as the fish went about their business in the virtual reality set-up.
The imaging caught an entire circuit in action. This circuit involves the inferior olive and cerebellum.
The cerebellum (little brain) is known to play a role in maintaining balance and posture, coordination of voluntary movements, motor learning and cognitive functions in humans.
The study found that the inferior olive contains information about the animal’s current location. This signal is transmitted to the cerebellum, which enables the fish to move back to the starting point.
When the team blocked these signals, the fish could not navigate back to its original location, showed the study.
“We found that the fish is trying to calculate the difference between its current location and its preferred location and use this difference to generate an error signal,” En Yang from the Janelia Research Campus, Howard Hughes Medical Institute, and first author of the new study, said in a statement.
The brain, he added, sends that error signal to its motor control centres (which control movements) so the fish can correct after being moved by flow unintentionally, even many seconds later,” he added.
The researchers initially expected to see the hippocampus in the forebrain light up. This part of the brain is known to help with memory and learning.
These findings open up a new investigation, where researchers can study if the same networks are at play in humans and other mammals.
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