Perte sensorielle et réorganisation cérébrale

Abstract

Qu’advient-il lorsqu’un individu perd la vue et que les informations visuelles ne parviennent plus aux régions cérébrales dédiées à leur traitement ? Ces régions deviennent-elles désuètes ? Arrêtent-elles de contribuer aux processus sensoriels et cognitifs ? Non. Les connaissances actuelles suggèrent que le cerveau se réorganise et rallie ces régions afin de traiter des stimulus non-visuels. Notre laboratoire se consacre depuis plusieurs années à l’étude de la cécité et des conséquences qui lui sont associées, tant sur le plan comportemental que sur celui de la réorganisation cérébrale.

It is without a doubt that humans are first and foremost visual beings. Even though the other sensory modalities provide us with valuable information, it is vision that generally offers the most reliable and detailed information concerning our immediate surroundings. It is therefore not surprising that nearly a third of the human brain processes, in one way or another, visual information. But what happens when the visual information no longer reaches these brain regions responsible for processing it ? Indeed numerous medical conditions such as congenital glaucoma, retinis pigmentosa and retinal detachment, to name a few, can disrupt the visual system and lead to blindness. So, do the brain areas responsible for processing visual stimuli simply shut down and become non-functional ? Do they become dead weight and simply stop contributing to cognitive and sensory processes ? Current data suggests that this is not the case. Quite the contrary, it would seem that congenitally blind individuals benefit from the recruitment of these areas by other sensory modalities to carry out non-visual tasks. In fact, our laboratory has been studying blindness and its consequences on both the brain and behaviour for many years now. We have shown that blind individuals demonstrate exceptional hearing abilities. This finding holds true for stimuli originating from both near and far space. It also holds true, under certain circumstances, for those who lost their sight later in life, beyond a period generally believed to limit the brain changes following the loss of sight. In the case of the early blind, we have shown their ability to localize sounds is strongly correlated with activity in the occipital cortex (the location of the visual processing), demonstrating that these areas are functionally engaged by the task. Therefore it would seem that the plastic nature of the human brain allows them to make new use of the cerebral areas normally dedicated to visual processing.