Brain compass implant gives blind rats "psychic" GPS
Brain compass implant gives blind rats psychic GPS
17:00 02 April 2015 by Andy Coghlan
Who needs sight to get around when you've got a digital
compass in your head? A neuroprosthesis that feeds geomagnetic signals into the
brains of blind rats has enabled them to navigate around a maze.
The results demonstrate that the rats could rapidly learn
to deploy a completely unnatural "sense". It raises the possibility
that humans could do the same, potentially opening up new ways to treat
blindness, or even to provide healthy people with extra senses.
"I'm dreaming that humans can expand their senses
through artificial sensors for geomagnetism, ultraviolet, radio waves,
ultrasonic waves and so on," says Yuji Ikegaya of the University of Tokyo
in Japan, head of the team that installed and tested the 2.5-gram implant.
"Ultrasonic and radio-wave sensors may enable the next generation of
human-to-human communicationMovie Camera," he says.
Psychic GPS
The neuroprosthesis consists of a geomagnetic compass – a
version of the microchip found in smartphones – and two electrodes that fit
into the animals' visual cortices, the areas of the brain that process visual
information.
Whenever the rat positioned its head within 20 degrees
either side of north, the electrodes sent pulses of electricity into its right
visual cortex. When the rat aligned its head in a southerly direction, the left
visual cortex was stimulated. The stimulation allowed blind rats to build up a
mental map of their surroundings without any visual cues.
During training, blind rats equipped with digital
compasses improved at finding food rewards in a five-pronged maze, despite
being released from one of three different arms of the maze at random each
time.
After two days and 60 maze trials, they could navigate
their way to the reward as fast as sighted rats could. Blind rats with no
additional senses, by contrast, were much slower to locate the reward and
didn't show any improvement. If they were relying on their sense of smell to
find the food then all three groups would have shown similar abilities.
As further evidence that the rats weren't simply checking
each of the maze arms in turn, the team looked at what the rats did at the
first turn they came across. The blind rats always went straight, no matter
where they started, suggesting that they were using a fixed foraging strategy.
The sighted rats and the compass-equipped rats varied their behaviour depending
on where they started from, suggesting they had a map in their head that they
were able to rotate depending on their location.
The rats were equally adept at navigating when electrical
pulses were fed into the part of the brain that registers whisker touch,
suggesting that even non-vision senses can be redeployed for navigation.
Sensory extension
Ikegaya says he has no idea how the implanted rats are
"seeing" their way around. But he says that the outcome shows how
adaptable the brain is. "Perhaps we don't make full use of our brain
because of the poor sensory organs it relies on," he says. Perhaps if we
could tap into its extra capacity, the real sensory world could be a lot more
colourful than we currently experience, he speculates.
Other researchers agree that such sensory extensions
might be feasible. "In theory, it would be possible to augment human
perceptual capabilities using this approach, but many more studies in animals
have to be done before one can justify any human study," says Miguel
Nicolelis of Duke University in Durham, North Carolina, who demonstrated two
years ago that rats with a brain implant can learn to "touch"
infra-red radiation Movie Camera.
People with paralysis who use a computer interface
implanted in their brain to communicate or move their limbs, for example, get
accustomed to using them without thinking, says Christopher James, a biomedical
engineer at the University of Warwick, UK. This may be what is happening in the
rats. "There's evidence to show that such stimulation becomes
'second-nature'," he says.
Journal reference: Current Biology, DOI:
10.1016/j.cub.2015.02.063
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