Looking into Task-Specific Activation Using a Prosthesis Substituting Vision with Audition
Figure 5
Brain activation foci elicited by control (dots comparison) and experimental tasks (localization or orientation processing) through a visual-to-auditory sensory substitution device (SSD) in blindfolded sighted subjects. The statistical parametric maps for these comparisons (in a random-effects analysis in the group) were superimposed on the axial, coronal, and sagittal section of an individual normalized brain MRI. Only voxels exceeding a threshold of corrected for false discovery rate (FDR) at the whole brain level were displayed according to the color scales that code the -values. (a) Brain activation observed in control condition, that is, in the contrast {control minus rest}. A bilateral activation in auditory brain areas was evident in this contrast. (b) Brain activation foci observed during the localization condition, that is, in the contrast {localization minus control masked (inclusive) by localization minus rest}. A bilateral activation in frontal brain areas and in the dorsal visual pathway was observed in this contrast. The images were displayed at the level of the inferior parietal lobule (BA 40), which was bilaterally recruited with a main focus in the left hemisphere, with a value of 4.76 at coordinates ( (mm) = −42, −52, 50). (c) Brain activation foci observed during the orientation condition, that is, in the contrast {stimulus orientation minus control masked (inclusive) by stimulus orientation minus rest}. This contrast elicited a left lateralization of brain activation in the dorsal visual pathway, with a main focus in the left inferior parietal lobule (BA 40), with a value of 4.75 at coordinates ( (mm) = −40, −50, 46). A bilateral recruitment of frontal brain areas was also observed. (d) Brain activation foci common to both spatial processing tasks with the SSD, that is, from a conjunction analysis of experimental conditions {localization minus control and orientation detection minus control}. The common neural substrate for localization and orientation processing with the SSD involved frontal brain areas bilaterally, including the inferior, middle, and superior frontal gyri, and parietal structures located in the left hemisphere such as the precuneus and the inferior and superior parietal lobules (see Table 2 for the detailed list of the activation foci). This part of the figure focused on the left inferior parietal lobule, with a value of 5.50 at coordinates ( (mm) = −30, −50, 48). Coordinates are in reference to the Talairach and Tournoux atlas [21] and the MNI template (see Section 2). L: left side of the brain.
