Functional and microstructural neurosubstrates between apathy and depressive symptoms in dementia

Area of Science:

• Neuroimaging
• Neurology
• Psychiatry

Background:

• Depressive symptoms and apathy frequently overlap in dementia, complicating clinical diagnosis.
• Understanding the distinct neurobiological underpinnings of apathy and depression in dementia subtypes is crucial.
• Alzheimer's disease (AD) and subcortical ischemic vascular disease (SIVD) are common dementia subtypes with overlapping symptoms.

Purpose of the Study:

• To differentiate the neurosubstrates of apathy and depressive symptoms in dementia using dual-modal MRI.
• To investigate the distinct brain network alterations associated with apathy and depression in AD and SIVD patients.

Main Methods:

• Ninety-two dementia patients (AD and SIVD) and 30 controls underwent MRI scans.
• Evaluated apathy using the Apathy Evaluation Scale (AES) and depression using Beck's Depression Inventory (BDI).
• Analyzed resting-state functional MRI (fALFF) and diffusion kurtosis imaging (MK) to identify brain hubs and network changes.

Main Results:

• Fractional amplitude of low-frequency fluctuation (fALFF) showed widespread changes in default mode network (DMN) and frontoparietal network (FPN) for apathy, and additionally salience network (SAN) for depression.
• Mean kurtosis (MK) revealed focal changes within DMN and SAN for both apathy and depression.
• fALFF correlated more with DMN/FPN in apathy and SIVD, while MK correlated more with specific regions (anterior cingulate, insula) in apathy and AD, indicating distinct patterns.

Conclusions:

• Dual-modal MRI (fALFF and MK) can differentiate the distinct neuropathological bases of apathy and depressive symptoms in dementia.
• Apathy and depression exhibit distinct patterns of brain network involvement and regional alterations in AD and SIVD.
• These findings support the use of advanced neuroimaging techniques for precise diagnosis and understanding of neuropsychiatric symptoms in dementia.