Random-effects analyses were conducted on the normalized maps for the group of six younger control subjects and (separately) for the group of six older control subjects. To determine the ROIs that were implicated in each paradigm, we conducted a mixed-effects analysis on the normalized activation maps for these groups of subjects, so that those clusters that were significantly implicated during the experimental protocol were identified. The clusters of activated voxels were localized to brain regions that are commonly recognized as part of the visuospatial network, including the left and right FEFs, SMA/SEFs, left and right parietal lobules along the IPS, and visual cortical regions (V1, V2, and V3 and V5/MT). Because the paradigms do not separate activation between V2 and V3, the regions of V2 and V3 were combined. Based on these analyses and the resultant activation maps and the neuroimaging literature reporting tasks similar to those used in these experiments, we defined the anatomic boundaries of these ROIs to characterize the extent of task-related activation. These regions were first identified on the averaged anatomic image from the left and right FEFs and were defined to include the precentral sulci and immediately adjacent gyri.
33 The SMAs, including the SEFs were identified as the tissue anterior to the precentral sulcus along the medial frontal lobes and posterior to the caudate nucleus.
34 The superior parietal lobule was drawn superior to the IPS and posterior to the postcentral sulcus,
34 35 left and right superior parietal lobule (superior and anterior to the intraparietal sulcus and posterior to the postcentral sulcus),
35 left and right inferior parietal lobule (inferior and posterior to the intraparietal sulcus including the supramarginal gyrus),
36 primary and secondary visual cortices (along the calcarine fissure to the cuneus and lingual gyrus),
37 tertiary visual cortex (from the borders of V1/V2 to the middle occipital gyrus),
37 and fusiform gyrus (from the mammillary body to the anterior tip of the parieto-occipital sulcus).
38 We broadly defined the PFC using Brodmann’s definitions to include the area between the superior rostral sulcus and inferior rostral sulcus and dorsally by the anterior cingulate. These ROIs were then applied to the individual data so that the number of interpolated voxels (volume of activation) could be calculated for each ROI for each subject for each paradigm.