General cortical activation in the three participant groups. Superimposed images on 3-D MRI represent cortical activation in the verbal fluency task (a) and visuospatial task (b). Upper figures show the activation of the frontal cortex, and lower figures show the activation of the parietal cortex. The color bar indicates [oxy-Hb] (mM·cm). Note that the scale of the color bar differs between figures (a) and (b). Abbreviations: HC, healthy controls; D, depression; AD, Alzheimer’s disease; [oxy-Hb], oxygenated hemoglobin concentration.