This cyborg fish is teaching us how your brain handles navigation

No, this isn't the aquatic version of the Chelsea Flower Show. The hat-wearing goldfish above is actually one of the stars in a new study finally explaining how the animals navigate in water.

This “cyborg fish”, as Ronen Segev – professor at Israel's Ben-Gurion University – calls it, was one of several used in the study. “Studying fish present a real opportunity for brain science,” Segev told BBC Science Focus – and apparently it’s all because of that hat.

Navigation is vital to finding food and shelter and escaping from predators. And it's not straightforward: navigating involves learning the environment, embedding information about that environment in the brain, and then retrieving it when needed. In fact, despite their reputation for having a bad memory, Segev explains, fish actually learn and remember their environment in order to navigate it better. We've been unaware of exactly how this works – until now.

The researchers used recording devices to measure a neuron in a part of the fish's brain that is associated with navigation while it swam along channels in a fish tank. This helped the researchers identify boundary vector cells (cells that respond to an animal's direction and distance from a boundary) that are similar to those found in mammals. However, unlike mammals, the goldfish's boundary vector cells allow it to move in ‘three-dimensional’ environments.

Humans don’t, of course, live in a cartoon-like world – but unlike terrestrial creatures, fish must navigate horizontally, diagonally and vertically.

So what’s actually in the hat? What looks like a stack of luggage is actually electronics that capture the neural signal, amplify it and then store it on a memory chip. The researchers then used the data to plot the fish's neuron activity against its motion detected by a camera in front of the tank.

According to Segev, the benefit of working with fish is that this hat effectively becomes a floating device in water rather than weighing the fish down – causing no disturbance to its swimming.

The study published in PLOS Biology shows that goldfish navigation is comparable to rats, suggesting that mammals share some navigational tools with fish. Given that mammals and fish separated off into a different evolutionary stream from mammals billions of years ago, these results may aid our understanding of the navigation system in human brains.

The next step for the researchers will be sending the cyborg fish into the semi-natural environment of a pond. Here, they will track the neuron activity of the fish while they interact in a larger environment – including with other fish. Apparently, Segev says, other fish aren't too bothered by the cyborgs: "They don't seem to care. We initially thought the device might weaken the fish and that it might be attacked by others, but it didn't happen."

He adds: "Fish are extremely important for the environment – so it is important that we understand their physiology, the way they behave and how they do it.

"Navigation helps us learn about understanding, learning and memory which is why it is such an important aspect of behaviour and brain science."