Head-mounted sensor helps blind rats navigate

3 Apr

A new study reveals how a head-mounted, compass-like device connected to the brains of blind rats allowed the animals to navigate a maze almost as well as normal-sighted rats, and the researchers say a similar technique could be used to aid navigation in blind humans.
A rat wearing a head-mounted sensor device
The head-mounted sensor was found to effectively guide blind rats through mazes.
Image credit: Yuji Ikegaya and Hiroaki Norimoto

Yuji Ikegaya and Hiroaki Norimoto, both of the University of Tokyo in Japan, published the details of their creation in the journal Current Biology.

According to the World Health Organization (WHO), approximately 39 million people worldwide are blind. Of these, 82% are aged 50 and older.

As well as the ability to see, blindness interferes with an individual’s spatial awareness, or “allocentric sense.” That is, a person’s ability to recognize the position of their body relative to their surroundings.

For their study, Ikegaya and Norimoto set out to see whether they could restore the allocentric sense of “blind” adult rats by stimulating the visual cortex in their brains. The rats were made blind through eyelid suturing.

The duo created a lightweight head-mountable sensor device consisting of a digital compass – the same as those found in smartphones – that is connected to a microstimulator with two electrodes.

Once implanted in the visual cortex of the rats’ brains, the device is able to detect their head movements and generate an electrical stimulation, or a “geomagnetic signal,” that informs the animals of which direction they are facing.

Device allowed blind rats to navigate maze almost as well as normal-sighted rats

The researchers set out to test whether the device could guide the blind rats through a maze, effectively restoring their allocentric sense.

With the devices attached, the rats were trained to seek food pellets in a T-shaped maze, as well as more complicated maze shapes. Their ability to solve each maze was compared with that of normal-sighted rats, which were able to depend on visual cues to reach the food pellets.

Ikegaya and Norimoto found that within 2-3 days of maze training, the blind rats learned to use the geomagnetic signal triggered by the device to find the food pellets. “Their performance levels and navigation strategies were similar to those of normal-sighted, intact rats,” the duo reports. “Thus, blind rats can recognize self-location through extrinsically provided stereotactic cues.”

The researchers say these findings demonstrate how the mammalian brain is able to learn and adapt to new information well into adulthood. Ikegaya says:

“The most remarkable point of this paper is to show the potential, or the latent ability, of the brain. 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.”

As a result, the team believes the findings could be applied to humans. Geomagnetic sensors could be attached to the walking sticks of blind individuals, for example, helping them to navigate their surroundings.

Based on their findings, the researchers say a geomagnetic sensor device similar to the one used in their study may be effective for restoring allocentric sense in blind people. What is more, artificial sensors could even be used to detect ultraviolet (UV) radiation and ultrasound waves.

“Perhaps you do not yet make full use of your brain,” Ikegaya hypothesizes. “The limitation does not come from your lack of effort, but it does come from the poor sensory organs of your body. The real sensory world must be much more ‘colorful’ than what you are currently experiencing.”

Medical News Today recently reported on a study detailing the creation of eyedrops that can allow users to see people and symbols up to 50 m away in the dark.