Grey matter hypometabolism and atrophy in Parkinson’s disease with cognitive impairment: a two-step process
Bibliographic record
Abstract
The pathophysiological process underlying cognitive decline in Parkinson's disease is not well understood. Cerebral atrophy and hypometabolism have been described in patients with Parkinson's disease and dementia or mild cognitive impairment with respect to control subjects. However, the exact relationships between atrophy and hypometabolism are still unclear. To determine the extension and topographical distribution of hypometabolism and atrophy in the different cognitive states of Parkinson's disease, we examined 46 patients with Parkinson's disease (19 female, 27 male; 71.7 ± 5.9 years old; 14.6 ± 4.2 years of disease evolution; modified Hoehn and Yahr mean stage 3.1 ± 0.7). Cognitive status was diagnosed as normal in 14 patients, as mild cognitive impairment in 17 and as dementia in 15 patients. Nineteen normal subjects (eight female, 11 male; 68.1 ± 3.2 years old) were included as controls. (18)F-fluorodeoxyglucose positron emission tomography and magnetic resonance imaging scans were obtained, co-registered, corrected for partial volume effect and spatially normalized to the Montreal Neurological Institute space in each subject. Smoothing was applied to the positron emission tomography and magnetic resonance imaging scans to equalize their effective smoothness and resolution (10 mm and 12 mm full-width at half-maximum and Gaussian kernel, respectively). Z-score maps for atrophy and for hypometabolism were obtained by comparing individual images to the data set of control subjects. For each group of patients, a paired Student's t-test was performed to statistically compare the two Z-map modalities (P < 0.05 false discovery rate corrected) using the direct voxel-based comparison technique. In patients with mild cognitive impairment, hypometabolism exceeded atrophy in the angular gyrus, occipital, orbital and anterior frontal lobes. In patients with dementia, the hypometabolic areas observed in the group with mild cognitive impairment were replaced by areas of atrophy, which were surrounded by extensive zones of hypometabolism. Areas where atrophy was more extended than hypometabolism were found in the precentral and supplementary motor areas in both patients with mild cognitive impairment and with dementia, and in the hippocampus and temporal lobe in patients with dementia. These findings suggest that there is a gradient of severity in cortical changes associated with the development of cognitive impairment in Parkinson's disease in which hypometabolism and atrophy represent consecutive stages of the same process in most of the cortical regions affected.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".