Researchers have given blind rats a fresh sense of direction by connecting tiny digital compasses to their brains.
The study by Japanese scientists shows that the animals learned quickly to use the unfamiliar signals to find their way around the world.
The team from the University of Tokyo believe that similar brain implants could one day help blind people navigate more easily, though a nearer-term prospect might be walking canes fitted with compasses that broadcast the direction they are pointing in.
Before the operation, the blind animals flunked a maze test, but they scored nearly as highly as sighted rats after a few days practice with the compass.
Writing in the journal, Current Biology, the researchers describe how they attached the compasses, of the sort found in smartphones, to the heads of rats that had their eyelids sewn shut. The compass was connected to a microstimulator that sent different electrical signals to the rat’s visual cortex when they were pointing north or south.
Before the implant was switched on, the rats performed badly at a navigation test that required them find some food. But after two days of the compass being switched on, the animals reached a success rate of more than 80%. When the device was switched off again, their performance dropped again.
“We were surprised that rats can comprehend a new sense that had never been experienced, or explained by anybody, and can learn to use it in behavioural tasks within only two to three days,” said Yuji Ikegaya, a senior author on the study.
Ikegaya said the aim of the research was not to restore the rats’ vision, but their “allocentric sense”, which allows animals and people to work out the position of their body in the world. What was unclear was whether the animals could learn to make sense of the directional signal from the compass.
Encouraged by the findings, the scientists speculate that humans could learn to use signals not only from geomagnetic compasses, but also from ultraviolet light, ultrasound waves and other forms of information. “The real sensory world must be much more colourful,” said Ikegaya.
In 2013, Miguel Nicolelis, a pioneer in brain-computer interfaces at Duke University in North Carolina, performed similar experiments that gave rats the ability to see heat, or infrared radiation. The closer the rats got towards an infrared lamp, the stronger the signals their brains received. As in the Japanese team’s work, the rats soon learned to use information to help find their way around.
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