Rats can navigate mazes, even when blind

With a compass-microchip prosthetic wired into their brains, blind rats can learn to navigate complex mazes to find food. What’s more, they can do it nearly as well as rats that still have their sight, researchers from Japan report April 20 in Current Biology. Success using the prosthetic demonstrates the flexibility of the brain to comprehend a completely new sense, they say. The result may lead to improved therapies for human blindness and to the enhancement of human senses beyond the standard five.

“These rats are learning and really learning fast,” says neurophysiologist Peter König of Osnabrück University in Germany. He adds that it’s pretty cool that the animals can learn to use the signals from the geomagnetic device in a meaningful way.

Study coauthor Yuji Ikegaya of the University of Tokyo says the rats may not perceive the meaning of direction as humans do. But, he says, the results do suggest that the animals can develop an internal map from a sense that isn’t inherent.

In previous studies, scientists manipulated ferrets’ senses so they could interpret visual cues with brain pathways originally wired for sound. Researchers have also developed a brain prosthetic that helps rats detect infrared light, which is usually invisible. In the new study, Ikegaya and Hiroaki Norimoto, also of the University of Tokyo, tested whether their prosthetic brain compass could help blind rats regain their ability to recognize the position of their bodies within mazes. Food was the incentive. To prevent the rats from using their sense of smell to find food, the scientists sprayed the odor of the food pellets all over the walls of the mazes.

The scientists then put the rats through 20 trial runs a day in a T-shaped maze. Relying on their vision, normal rats learned where food was hidden and how to consistently get back to it within a week. The normal rats had similar success in a five-armed maze. Blind rats did not have such success unless they had a prosthetic brain compass.

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The prosthetic is made of a digital compass, microchip and tiny electrodes. Ikegaya and Norimoto first implanted the electrodes into the brain region responsible for vision. When the digital compass sensed a blind rat’s head pointed north, the microchip transferred data to the right electrode and it pulsed. When the rat’s head pointed south, the left electrode pulsed. With the stimulation, the blind rats learned to navigate the maze and find food in roughly the same number of trials as rats with intact vision. Even after the compass was turned off when the blind rats entered the maze, they could still orient themselves and find the food.

Blind rats that had the electrodes implanted in the region of the brain responsible for touch performed equally well.

König says the result supports the idea that senses are not innate. The brain learns how to handle the senses, and it can do it with information that is not limited to sight, sound, taste, touch and smell. This adaptability of the brain is how the whole idea of substituting and enhancing the senses got started, König says. He notes that the new prosthetic directly augments the rats’ senses, an advance that may offer a better look at how the brain changes at the cellular level when given new sensory information.

Ikegaya says the results could be used in an immediate and practical way to advance the development of the canes that blind people use when walking. One idea is to incorporate the compass into the cane. When the person pushes a button on the top of the cane, it could signal the direction of north through vibrations. “This is very simple,” Ikegaya says, “but it would greatly help the blind to walk.”

He notes that scientists might also be able to use the information to give humans super-sensing abilities. “Sensing ultraviolet light may be important for reducing skin cancer,” Ikegaya says. “Sensing ultrasonic and radio waves may enable a next-generation form of human-to-human communication.”