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Changes in parahippocampal white matter integrity in amnestic mild cognitive impairment: a diffusion tensor imaging
E J Rogalski1, C M Murphy, L deToledo-Morrell
1Cognitive Neurology and Alzheimer's Disease Center at Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.
Abstract:
In the present study, changes in the parahippocampal white matter (PWM), in the region that includes the perforant path, were investigated, in vivo, in 14 individuals with amnestic mild cognitive impairment (aMCI) compared to 14 elderly controls with no cognitive impairment (NCI). For this purpose, (1) volumetry; (2) diffusion tensor imaging (DTI) derived measures of mean diffusivity (MD) and fractional anisotropy (FA); and (3) tractography were used. In addition, regression models were utilized to examine the association of PWM measurements with memory decline. The results from this study confirm previous findings in our laboratory and others, showing that compared to controls, individuals with aMCI have PWM volume loss. In addition to volume reduction, participants with aMCI demonstrated a significant increase in MD, but no difference in FA, both in the PWM region and in fibers modeled to pass through the PWM region. Further, the DTI metric of MD was associated with declarative memory performance, suggesting it may be a sensitive marker for memory dysfunction. These results indicate that there is general tissue loss and degradation (decreased volume; increased MD) in individuals with aMCI compared to older people with normal cognitive function. However, the microstructural organization of remaining fibers, as determined by measures of anisotropic diffusion, is not significantly different from that of controls.
Insights
Individuals with amnestic mild cognitive impairment (aMCI) show parahippocampal white matter (PWM) volume loss and increased diffusivity, indicating tissue degradation. Microstructural organization of remaining fibers remains unchanged compared to controls.
Area of Science:
- Neuroscience
- Neuroimaging
- Cognitive Science
Background:
- Mild cognitive impairment (MCI) is a transitional stage between normal aging and dementia.
- The parahippocampal white matter (PWM), including the perforant path, is crucial for memory function.
- Understanding microstructural changes in PWM is vital for early detection of cognitive decline.
Purpose of the Study:
- To investigate in vivo changes in parahippocampal white matter (PWM) in individuals with amnestic mild cognitive impairment (aMCI).
- To compare PWM volume, diffusion tensor imaging (DTI) metrics, and tractography between aMCI patients and normal cognitive impairment (NCI) controls.
- To examine the association between PWM measurements and memory decline.
Main Methods:
- Volumetry was used to assess PWM volume.
- Diffusion tensor imaging (DTI) provided measures of mean diffusivity (MD) and fractional anisotropy (FA).
- Tractography and regression models were employed to analyze white matter integrity and its relation to memory performance.
Main Results:
- Individuals with aMCI exhibited significant PWM volume loss compared to NCI controls.
- aMCI participants showed increased MD in the PWM region, suggesting tissue degradation.
- No significant differences in fractional anisotropy (FA) were observed, indicating preserved microstructural organization of remaining fibers.
Conclusions:
- The study confirms tissue loss and degradation in the PWM of individuals with aMCI.
- Increased MD in PWM is a sensitive marker associated with memory dysfunction in aMCI.
- While volume and diffusivity change, the microstructural organization of remaining white matter fibers is largely preserved.
