[Sensory loss and brain reorganization].
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.
Fortin
Madeleine
M
Centre de Recherche, Centre Hospitalier Universitaire Mère-Enfant (Sainte-Justine), Université de Montréal, CP 6128 - Succursale Centre-ville, Montréal (Québec), H3C 3J7Canada.
Voss
Patrice
P
Lassonde
Maryse
M
Lepore
Franco
F
D001307:Auditory Perception; D001921:Brain / Q000473:pathology / Q000502:physiology* / Q000503:physiopathology; D001931:Brain Mapping; D006801:Humans; D009473:Neuronal Plasticity; D012678:Sensation Disorders / Q000503:physiopathology*; D014786:Vision Disorders / Q000503:physiopathology*; D014796:Visual Perception