Neural networks of top-down and bottom-up attention in early onset blindness

Recent functional neuroimaging studies have revealed that occipital or visual cortical areas in individuals blinded in o_r around birth are metabolically active during tactile, auditory and cognitive stimulation. These findings suggest that in the early blind (EB) the areas that are normally engaged by visual stimulation process non-visual information (a phenomenon referred to as cross-modal reorganization). However, the functional significance of occipital (Occ) activity in this population is not well understood. The aim of my dissertation was to determine whether different mechanisms of attention influence neural activity within Occ cortical regions in the EB. Identifying the functional domains that activate the Occ cortex in the EB will lead to a better understanding of the influences important for the establishment of cross-modal reorganization. In addition, EB results in superior performance on a number of auditory and tactile behavioral tasks relative to sighted counterparts (SC). A second goal was to determine whether EB relative to SC individuals show enhanced attentional abilities within auditory and tactile domains. This approach would allow me to determine whether an association exists between activity within the Occ cortex of the EB and alterations in attentional abilities. Event-related functional magnetic resonance imaging (erfMRI) was combined with oddball, target detection tasks. Oddball tasks tap into various attentional mechanisms because they require the selection of a specific, infrequent target stimulus presented within a train of repeating and identical standard stimuli. Attention is generally considered a mechanism that resolves conflict between competing sensory signals such