(ORDO NEWS) — For orientation in the world, people rely primarily on sight and hearing. Our eyes and ears complement the highly developed neural circuits of the brain that perceive and analyze the signals coming from them.
Fish are much simpler, but they have feelings unfamiliar to people – including the ability to accurately sense the flow of water. To a certain extent we perceive them, and even bacteria, but in fish and amphibians this feeling reaches inaccessibility to us.
This ability is critical for effective swimming and survival, it allows you to save energy, avoid predators and find prey, stay in packs or alone. However, until now, the neural circuits of fish associated with the registration of signals about water currents were unknown. Only recently, Australian neurophysiologists did this work under the supervision of a professor at the Queensland Institute of the Brain, Ethan Scott.
To do this, scientists used “ calcium imaging, ” a relatively new microscopy technique that allows nerve cell activity to be recorded by a fluorescent signal that is triggered in response to an influx of calcium ions. The method made it possible to visualize the work of neurons of young zebrafish , which, under controlled conditions, were exposed to water currents flowing around their bodies in different directions.
“We checked two directions of the flow, from head to tail – as when swimming forward – and from tail to head – as when trying to swallow it with a predator,” the authors explain , “and found that some neurons respond in both directions, and some work specifically, only in one of them.”
So, the cells in the ganglia of the lateral line – the organ that perceives the currents of water – simply activated in response to the flow. But neurons receiving signals from them have already identified the direction and speed of the current.
According to scientists, these neurons were found in many areas of the fish brain, including some that had not previously been associated with the perception of water currents. “By tracking thousands of neurons and their activity over time, we were able to register their reaction to the course and determined the functional circuits that they form in the fish’s brain,” the authors conclude. Their article is published in the latest issue of the Journal of Neuroscience.
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