published in Forum Express
12 décembre 2007
'The only limits with this device are the ones set by the researcher': Daniel Chebat
“It’s the first time I make my way across a cluttered course of several meters without the help of my cane,” explains 35-year-old M.L. who has been blind since birth. He accomplished this thanks to a device mounted on his tongue, which creates a mental image of the space around him.
In a video recorded by Daniel Chebat, PhD student in experimental neuropsychology at the Université de Montréal School of Optometry, M.L. is seen making his way down a hallway while avoiding a block on his left, a pipe on his right and the low wall by his feet. This is possible thanks to a camera mounted on his glasses which transmits images to a 144-pixel unit on his tongue.
The Tongue Display Unit (TDU) was tested for the first time in the summer of 2006 on a 14-meter course in Montreal. It proved to be remarkably efficient. “The 15 blind people from birth we tested showed extraordinary ability after just a few hours of training,” explains the 28-year-old Chebat. M.L., an engineer himself, said he looked forward to having a similar device, while other test subjects added that such a device could eventually replace their white cane.
Chebat explains that this is not about making the blind see. The vision of the blind is not modified by the TDU and remains at approximately 1/90. But the TDU allows them to recognize simple shapes in their surrounding environment thanks to the electrical charges transmitted on their taste buds.
“We are doing basic research and our experiment confirms what we intended to demonstrate regarding the activation of the visual cortex. It’s fascinating: the brain of the blind processes the data coming from the TDU as if it were visual data,” explains Chebat who works under the supervision of Professor Maurice Ptito who is well known for his work on neuronal plasticity.
The device used for this experiment was developed by Professor Paul Bach-y Rita of the University of Wisconsin-Madison and it quickly interested Professor Ptito. The success Ptito obtained won him international acclaim as well as substantial funding.
Ptito is the recipient of the Colonel Harland Sanders Chair in Vision Sciences. The funding allowed him to set up research labs and to build testing courses at the School of Optometry in Montreal and at the Hvidovre University Hospital in Denmark where teams of four people work under his supervision.
Chebat is currently leading three research projects in Canada and Denmark, which will eventually be the focus of scientific articles. The project in which M.L. participated is about to be published while the two other projects are still at the experimental stage.
In the second project, he wants to explore the sensory acuity of the blind within the confines of a complex course made up of five corridors. The third project, intends to immerse users of the TDU in a video game. The test subject will be asked to maneuver inside a virtual environment transmitted onto his taste buds while a scanner observes his brain.
The observation of the brain during use of the TDU has yet to be done. “The only limits with this device are the ones set by the researcher,” says Chebat who is thrilled by the development of his research.
514 343-6111 , extension 4532
Canadian Institutes of Health Research
Tuesday, February 26, 2008
For the second consecutive year my abstract was selected to be part of the press book release of the prestigious SfN meeting which took place in San Diego (Nov. 3-7th). Here is a copy of the abstract that was released to the media:
Navigation Skills in the Early Blind Using a Tongue Stimulator.
D-R. Chebat, C. Rainville, K. Madsen, O. Paulson, M., Ptito
Univ. Montreal, Montreal, Canada.
Danish research center fo Magnetic Resonance, Hvidovre Hospital, Hvidovre, Denmark
Program Number: 737.24
Session Date-Time:Tuesday Nov., 6, 1:00 PM
Navigation is a complex behavior involving a multitude of sensory modalities. Vision is an integral component in navigation, providing the traveler with information about the configuration of proximal and distal space as well as updating motion cuess. The hippocampus has been shown to be involved in visual spatial memory in primates and humans. This brain structure comprises cells that respond to locations that are called place cells. Spatial navigation depends, in part, upon place celle actitivuty in teh hippocampus that plays a fundamental role in the interpretation of visual-based information. The hippocampus is subject to plastic changes humans. For example taxi drivers who have had an extensive visual navigational training show an enlarged right hippocampus whereas lesions to this same region impair retrieval and learning of spatial routes. Topographical memory relies on a network of brain regions involving the hippocampus, visual cortex, frontal lobes and parietal regions. Blind individuals from birth, however, are not impaired on a spatial competenmce level or in the formation of novel spatial maps of the environment when using tactile, proprioceptive or auditory cues. We recently showed, using a technique called Voxel-Based Morphometry (VBM) carried out on whole brain magnetic resonance imaging scans (MRI) that born blind people have a reduced right posterior hippocampus . The question therefore arisses on how blind people form spatial maps of their environment?
We first tested the ability of blind subjects to navigate in an obstacle course. Wearing a camera mounted on glasses and the tongue display unit (TDU) grid on the tongue, they were requested to point to the obstacle (detection), and move towards it and negotiate a path around it (avoidance). We shoed that blind subjects had no difficulty to peform teh task besides a structurally atrophied right posterior hippocampus (see 'Chebat et al., 2007a).
We proposed that they probably relied on other brain structures belonging to the neural network involved in topographical memory. We emphasied the use of neural pathways that connect teh parietal and frontal cortices to the occipital lobe because they are enlarged in the blind compared to the sighted. In a virtual maze task where subjects used their tongue to move along a virtual path while in a 3.0T fMRI scanner, we were able to show that route forming in the blind did not deoend upon the hippocampus but rather on cortical areas.
These results are of great interest since tehy show that the tongue is a useful organ to move around in the environment and to do so, it calls on a reorganization of brain connections that involve the frontal and parietal cortices. The applications of the TDU are therfore important since objects in the enviironment can be signaled to teh tongue in any non-vision situations lie darkness. Tests are currently on their way in deep sea divers wearing infra red goggles and tehir ability to use their tongue as a signal detector.