(Not in Brain Scans etc
Figure 25.1
(click for larger version of image)
Regions of overlapping activity for three groups of studies, superimposed on axial and sagittal slices of a normalized single-subject anatomical image. The overlap was calculated by averaging binarized contrast images indicating which voxels were significant for a given contrast (studies and contrasts are listed in Table 25.1).
The color scale indicates the percentage of studies showing activation in a given voxel. The same color scale (from 22 to 50% of overlap) is applied to all images.
Although no single voxel was shared by 100% of studies in a group, probably due variability across groups of subjects, laboratories, and imaging methods, Table 25.1 revealed a high consistency of activations. (A) The horizontal segment of the intraparietal sulcus (HIPS) was activated bilaterally in a variety of contrasts sharing a component of numerical quantity manipulation. The barycenter of the region of maximum overlap (> 50%) was at Talairach Coordinates (TC) 41, -42, 49 in the left hemisphere, and -48, -41, 43 in the right hemisphere. Activation overlap is also visible in the precentral gyrus. (B) The angular gyrus (AG) was activated with a strong left lateralization (TC -48, -59, 30), and activated in 4/5 studies. Posterior cingulate as well as superior frontal regions also show some degrees of overlap. (C) The posterior superior parietal lobule (PSPL) was activated bilaterally in a few numerical tasks (left and right barycenters at TC -26, -69, 61 and 12, -69, 61; and see Table 25.1).
To emphasize the non-specificity of this region, the image shows the intersection of the overlap between four numerical tasks with an image of posterior parietal activity during a non-numerical visual attention shift task (Simon et al., 2002).