To control for the effect of cardiovascular risk factors, subjects with a history or signs of hypertension, diabetes mellitus, and cardiac arrhythmia were excluded. The fasting plasma glucose level was less than 6.7 mmol/L (120 mg/mL) in all subjects included in the study, and electrocardiograms were normal. All selected subjects were normotensive—systolic blood pressures below 140 mm Hg and diastolic blood pressures below 90 mm Hg—except 3 subjects, 2 patients with AD and 1 control subject, who showed borderline systolic hypertension, with a systolic blood pressure of about 165 mm Hg and a diastolic blood pressure of less than 90 mm Hg. Intracerebral pathologic disorders, such as cerebral infarction, neoplasms, and chronic cerebrovascular lesions, were excluded for all subjects by normal MRI scans, other than the overall brain atrophy in the group with AD. Further substantial comorbidity, like focal neurological signs, hypothyroidism, and other pathologic conditions that may directly or indirectly influence cerebral structure and function were excluded in all subjects by history, physical and neurological examinations, psychiatric evaluations, chest x-ray films, electrocardiograms, electroencephalograms, brain MRI, and laboratory tests (complete blood count; sedimentation rate; serum electrolytes, glucose, urea nitrogen, creatinine, liver-associated enzymes, cholesterol, high-density lipoprotein, and triglyceride levels; antinuclear antibodies; rheumatoid factor; VDRL; human immunodeficiency virus test; serum vitamin B12 and folate levels; thyroid function tests; and urinalysis). In particular, no subject included in the study showed periventricular areas of hyperintensity (PVH) extending more than 10 mm in the deep white matter or hyperintense foci in the deep white matter larger than 10 mm in diameter. No hyperintense foci at the rostral and occipital parts of the CC were visible on the axial-sliced MRI scan. Total and regional WMH and PVH scores are shown in Table 2.