Grant: Operating Grant

The human brain shows remarkable capacities to modify its organization and function in response to external demands. In neurologically normal subjects, these changes occur during regular maturation and learning. In individuals with sensory loss due to damage to peripheral organs, such as in the blind, these normal changes are also accompanied by modifications that allow the individuals to adapt and possibly compensate for their loss. We have examined this problem using behavioural, electrophysiological and imaging studies and plan to continue and extend them in the present proposal. Thus, at the behavioural level, we plan to examine if blind subjects outperform sighted ones in voice discrimination and whether performance is related to stronger activation of brain structures that control for voice perception. We have shown in the past that they excel in auditory and tactile functions. We shall thus examine, using functional Magnetic Resonance Imaging if this is due to recruitment by auditory or tactile stimulation of the visual cortex that no longer receives visual inputs. We shall specifically examine the nature of this recruitment at three levels: a) by investigating whether it follows the specific function of the area or adapts to the functions of the sensory systems which they now treat, b) we shall try and define the mechanisms and pathways through which this occurs and d) we shall analyze whether these recruitments of visual areas are truly responsible for the superior abilities of the blind by temporarily inactivating the recruited visual structures, using Transcranial Magnetic Stimulation, and determining if performance is affected.