Tokyo: Scientists have discovered that blind rats with a geomagnetic compass hooked to the brain can navigate through a maze nearly as well as normally sighted rats, a finding that may help develop technology which allows visually-impaired humans to walk more freely.
"The most remarkable point of this paper is to show the potential, or the latent ability, of the brain," said Yuji Ikegaya of the University of Tokyo.
"That is, we demonstrated that the mammalian brain is flexible even in adulthood - enough to adaptively incorporate a novel, never-experienced, non-inherent modality into the pre-existing information sources," Ikegaya said.
In other words, he said, the brains of the animals they studied were ready and willing to fill in "the 'world' drawn by the five senses" with a new sensory input.
Ikegaya and his colleague Hiroaki Norimoto set out to restore not vision, but the blind rats' allocentric sense. Allocentric sense is what allows animals and people to recognise the position of their body within the environment.
What would happen, the researchers asked, if the animals could "see" a geomagnetic signal? Could that signal fill in for the animals' lost sight? Would the animals know what to do with the information?
The head-mountable geomagnetic sensor device the researchers devised allowed them to connect a digital compass (the kind found in any smartphone) to two tungsten microelectrodes for stimulating the visual cortex of the brain.
The very lightweight device also allowed the researchers to turn the brain stimulation up or down and include a rechargeable battery.
Once attached, the sensor automatically detected the animal's head direction and generated electrical stimulation pulses indicating which direction they were facing - north or south, for instance.
The blind rats were then trained to seek food pellets in a T-shaped or a more complicated maze. Within tens of trials, the researchers reported, the animals learned to use the geomagnetic information to solve the mazes.
In fact, their performance levels and navigation strategies were similar to those of normally sighted rats. The animals' allocentric sense was restored.
"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," Ikegaya said.
The findings suggest one very simple application: to attach geomagnetic sensors to the canes used by some blind people to get around.
The researchers expect, based on the findings, that humans could expand their senses through artificial sensors that detect geomagnetic input, ultraviolet radiation, ultrasound waves, and more.
The study is published in the Cell Press journal Current Biology.
