In the theory, brain recordings from rodents revealed that internal compasses are stored in specialised rings of neurons called ring attractor networks. It was believed that a precise internal compass needed a vast network with many neurons while a small network with few neurons would make the compass needle vibrate and produce errors.
It was only after that scientists learned about an internal compass in a tiny fruit fly.
”The fly’s compass is very accurate but it is based on a really small set of neurons which is very different from what was previously supposed,” says Janelia Group Leader Ann Hermundstad. ” So, there was clearly a gap in our understanding of brain compasses.”
Generating a ring attractor
When Noorman arrived at Janelia in 2019, she was presented with the problem Hermundstad and others had been puzzling over: What mechanism allows the fruit fly’s relatively tiny brain to produce such a reliable magnetic map?
Noorman first wanted to demonstrate that one could not create a ring attractor with a small network of neurons, and that one had to add ‘something else’ such as other types of cells and more complex and precise properties of the cells. To do that, she removed all the “extra stuff” from the existing models to see if she could create a ring attractor with what is left.
Thus, Noorman learned that with a different assumption, one can construct a ring attractor with only four neurons if the connections between them are properly set up. Noorman collaborated with other researchers at Janelia to prove the new theory experimentally: they provided physiological evidence that the fly brain is capable of creating a ring attractor.
Subsequently, the researchers would like to know if this ‘extra stuff’ could offer further stability to the ring attractor network and if the basic computation could help form a foundation for computations of more complex networks with multiple variables. More experiments could also be useful in determining the way the connections between neurons in the network are altered and the effects that sensory cues have on the network’s coding of head direction.
Noorman, a mathematician who became a neuroscientist said that while it has been difficult for her, it has been fun trying to determine how to turn biology into maths that has a solution.
“The fly’s head direction system is the first example of neural activity that I have ever seen. so it has been fun to actually figure out and understand how that works,” she says.
Reference:
Hughes H. Small brains can accomplish big things, according to new theoretical research Medical Xpress
