Can these eyes lie? At least they may be able to see magnetic fields, X-rays and Co in the future ... Image: Thinkstock
Whether it's Superman's X-ray vision or the ability to see magnetic fields - neuroscientist Miguel Nicolelis believes it's only a matter of time before magic is no longer magic even for ordinary people. Such an artificial sixth sense should be made possible by novel interfaces between brain and computer, so-called BCIs. The Brazilian has already taken a first step in this direction: he and his colleagues allowed rats to perceive the invisible infrared light - and that with the help of their sense of touch. It sounds rather idiosyncratic what the scientists working at Duke University in Durham, USA did with their rats: they implanted tiny electrodes in their brains, which were connected to an infrared sensor. Then they attached this detector to the forehead of the animals. As soon as he picked up a signal, such as from an infrared LED, he generated an electrical impulse, which in turn stimulated the cerebral cortex. However, the researchers placed their electrodes not in the visual center of the rat, but in an area where whisker touches are processed.

Reward beckons where it shines

The scientists then trained the rats to respond to light signals by placing them in a test box with various LEDs, initially turning on only those that produced light in the visible range. Over time, the rats learned to squeeze a lever wherever it shone. As a reward, there was a fresh drink of water. As the animals mastered this task, the scientists switched to infrared LEDs. At first, the rats apparently had difficulty with the unfamiliar signals in their brains, reports Nicolelis: They did not run to the active light-emitting diode, but scratched their faces. This shows that her brain interprets the electrical impulses as touch, at least at the beginning, he says.

Over time, however, that changed: the rats learned to associate the signals in their brains with the infrared LEDs. When they approached the light source, they repeatedly moved their heads back and forth in order to be able to pinpoint the source of the stimulus. After about a month, they were so good at it that they made almost no mistakes in choosing the correct light source. With the help of the BCI, they had developed a form of perception that they did not have before, explains the researcher. Thus, for the first time, a BCI was not used, as usual, to amplify or restore meaning, but to functionally expand or create a new meaning. display

Complete instead of replace

According to Nicolelis, this result shows how flexible the brain really is. Because the ability to perceive the infrared did not replace the sense of touch, which was localized in the same brain region. Rather, the stimulated cortex seems to have split up in order to perform both functions, the researcher reports: In the end, the rats were able to perceive the infrared light as well as to feel full contact with their whiskers. He therefore holds the hitherto common assumption that the stimulation of a particular type of nerve cells in the brain would always produce a certain, defined sensory impression, for wrong. Instead, the brain seems to be able to adjust to all sorts of new stimuli - even if they are based only on relatively unspecific electrical impulses.

What fascinates the scientist, however, is the great potential of the method. Of course, first of all, he dutifully notes that it could help many people who have lost parts of their brains due to injury or stroke. It is possible, for example, to direct signals from the eye to another region of the cortex after damage to the visual center, for example to the hearing center, so as to return the affected person their vision. But Nicolelis' visions go much further: he is sure that with time, neuroprostheses can be developed that allow a fully developed additional sense - and not just a diffuse perception as in the current test. With that you could let animals or humans see everything, from ultrasound to UV-light and radio waves to magnetic fields. Superman sends greetings.

Miguel Nicolelis (Duke University, Durham) et al.: Nature Communications, online pre-publication of 12 February © wissenschaft.de - Ilka Lehnen-Beyel

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