Hippocampal and entorhinal structures in subjective memory impairment: a combined MRI volumetric and DTI study

Area of Science:

• Neuroimaging
• Gerontology
• Cognitive Neuroscience

Background:

• Subjective memory impairment (SMI) is prevalent in older adults and recognized as a risk factor for cognitive decline, mild cognitive impairment, and dementia.
• Early Alzheimer's disease pathology affects medial temporal lobe structures, specifically the hippocampus and entorhinal cortex.
• Understanding brain changes associated with SMI is crucial for early detection and intervention strategies.

Purpose of the Study:

• To investigate gray matter (GM) volume and microstructural changes in the hippocampus and entorhinal cortex in individuals with SMI.
• To compare these brain metrics between individuals with SMI and cognitively healthy elderly controls.
• To determine if combined imaging measures can improve classification accuracy between groups.

Main Methods:

• Utilized diffusion tensor imaging (DTI) and volumetric analysis to assess hippocampal and entorhinal regions.
• Compared gray matter volume and DTI measures (fractional anisotropy, mean diffusivity) between 18 participants with SMI and 27 elderly controls.
• Analyzed data from 45 participants with a mean age of 70.31 years.

Main Results:

• Individuals with SMI exhibited reduced entorhinal cortical volumes compared to controls.
• No significant differences in hippocampal volume were observed between the SMI and control groups.
• SMI participants showed microstructural alterations in the hippocampal body and entorhinal white matter, indicated by lower fractional anisotropy and higher mean diffusivity.

Conclusions:

• The entorhinal region demonstrates both macrostructural and microstructural changes in individuals experiencing SMI.
• The hippocampus shows only microstructural alterations in the presence of SMI.
• Combining entorhinal cortical volume and hippocampal fractional anisotropy enhances the ability to differentiate between individuals with and without SMI.