Abstract
BackgroundPatients with Alzheimer’s disease (AD) often present with apathy symptoms resembling the decreased motivation observed in depressed patients. Therefore, differentiating the initial phase of AD from late life depression may be difficult in some cases. Near-infrared spectroscopy (NIRS) is a functional neuroimaging modality that uses near-infrared light to measure changes in hemoglobin concentration on the cortical surface during activation tasks. The objective of this study was to investigate differences in brain activation associated with late life depression and with AD by means of NIRS.MethodsNIRS was performed in 30 patients with depression, 28 patients with AD, and 33 healthy controls, all aged 60 years or older. During two tasks, a verbal fluency task and a visuospatial task, changes in oxygenated hemoglobin concentration in the frontal and parietal cortices were investigated.ResultsIn the visuospatial task, cortical activation was lower in the depressed group than in the AD group, and significant differences were observed in the parietal cortex.ConclusionsNIRS can detect differences in brain activation between patients with late life depression and those with AD. NIRS is a promising tool for the differential diagnosis of late life depression and AD.
Highlights
Patients with Alzheimer’s disease (AD) often present with apathy symptoms resembling the decreased motivation observed in depressed patients
Clinical data Mini Mental State Examination (MMSE) and Frontal Assessment Battery (FAB) scores were decreased in the order of healthy controls, patients with depression, and patients with AD, confirming a decrease in cognitive function (Table 1)
MMSE and Clinical Dementia Rating (CDR) scores confirmed that the patients with AD were in the initial phase of the disease
Summary
Patients with Alzheimer’s disease (AD) often present with apathy symptoms resembling the decreased motivation observed in depressed patients. Careful observation of the clinical course may be required to differentiate late life depression from the initial phase of Alzheimer’s disease (AD). Depression-related and age-related factors mutually affect each other For this reason, late life depression tends to be accompanied by cognitive dysfunction and clinical symptoms are multifaceted, making diagnosis difficult. To discriminate depression from dementia, brain imaging may be a helpful addition to a detailed examination of the patient’s medical history and current findings. For this purpose, NIRS, a method for measuring brain function that was developed during the 1990s, is used to measure changes in regional cerebral blood flow (rCBF) associated with brain activation. The advantage of NIRS over other functional neuroimaging techniques such as fMRI is that subjects can be examined more in the sitting position
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