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Frontal Dysfunction Underlies Depression in Mild Cognitive Impairment: A FDG-PET Study
Hye Sook Lee1, Il Han Choo, Dong Young Lee
1Department of Neuropsychiatry, College of Medicine, Seoul National University, Seoul, Korea.
Objective:
Depression is a very common symptom in people with mild cognitive impairment (MCI), a preclinical stage of Alzheimer's disease (AD), and in those with clinically evident AD. Moreover, MCI individuals with depression show a higher conversion rate to clinical AD than those without depression. This study aimed to elucidate the functional neuroanatomical substrate of depression in MCI.
Methods:
Thirty-six patients were recruited from a University Hospital-based cohort; 18 of these subjects had MCI with depression (MCI_D); the remaining 18 subjects were age- and gender-matched, and had MCI with no depression (MCI_ND). For comparison, 16 cognitively normal (CN) elderly individuals were also included. All subjects underwent Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) scanning and regional cerebral glucose metabolism was compared among the three groups by a voxel-based method. The relationship between severity of depression, as measured by Hamilton Rating Scale for Depression (HRSD) scores, and glucose metabolism was also investigated.
Results:
MCI_D showed lower glucose metabolism in the right superior frontal gyrus than MCI_ND. There was a significant negative correlation between HRSD score and glucose metabolism at the same frontal region for overall MCI subjects. When compared with CN, both MCI_D and MCI_ND showed decreased glucose metabolism in the precuneus, while MCI_D had, in addition, reduced metabolism in other diffuse brain regions.
Conclusion:
Given previous observations on depression in AD, our results suggest that functional disruption of the frontal region, known to be associated with primary or other secondary depression, underlies depression in preclinical AD as well as clinically evident AD.
Insights
Depression in mild cognitive impairment (MCI) is linked to reduced glucose metabolism in the right superior frontal gyrus. This finding suggests frontal lobe dysfunction contributes to depression in both preclinical and clinical Alzheimer's disease (AD).
Area of Science:
- Neuroscience
- Gerontology
- Psychiatry
Background:
- Depression is prevalent in mild cognitive impairment (MCI) and Alzheimer's disease (AD).
- MCI with depression has a higher conversion rate to AD.
- The neuroanatomical basis of depression in MCI requires elucidation.
Purpose of the Study:
- To investigate the functional neuroanatomical differences in depression among individuals with MCI.
- To identify the brain regions affected by depression in MCI patients.
Main Methods:
- Compared regional cerebral glucose metabolism using Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) in three groups: MCI with depression (MCI_D), MCI without depression (MCI_ND), and cognitively normal (CN) elderly individuals.
- Utilized a voxel-based method for statistical comparison of glucose metabolism.
- Correlated depression severity (Hamilton Rating Scale for Depression - HRSD) with glucose metabolism.
Main Results:
- MCI_D patients exhibited lower glucose metabolism in the right superior frontal gyrus compared to MCI_ND patients.
- A negative correlation was found between HRSD scores and glucose metabolism in the frontal region for all MCI subjects.
- Both MCI_D and MCI_ND showed reduced metabolism in the precuneus compared to CN individuals; MCI_D also displayed reduced metabolism in other diffuse brain areas.
Conclusions:
- Functional disruption of the frontal region is associated with depression in MCI.
- These findings suggest that frontal lobe dysfunction underlies depression in both preclinical and clinically evident Alzheimer's disease.
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