Anteroposterior Hippocampal Metabolic Heterogeneity: Three-dimensional Multivoxel Proton<sup>1</sup>H MR Spectroscopic Imaging—Initial Findings
Bibliographic record
Abstract
PURPOSE: To quantify proton magnetic resonance (MR) spectroscopy-detectable metabolite concentrations along anteroposterior axis of hippocampus in healthy young and elderly subjects. MATERIALS AND METHODS: Young (three women, three men; age range, 25-35 years) and elderly (four women, two men; age range, 68-72 years) groups underwent MR imaging and proton MR spectroscopic imaging at 3 T in this HIPAA-compliant prospective study and gave institutional review board-approved written consent. Volume of interest was centered on and tilted parallel to hippocampal anteroposterior plane. Absolute N-acetylaspartate (NAA), choline, and creatine levels were obtained in each voxel, with phantom replacement. RESULTS: Mean NAA, creatine, and choline concentrations in the young group were higher in posterior hippocampus (12.9 mmol/L +/- 2.0 [standard deviation], 7.8 mmol/L +/- 1.2, 2.3 mmol/L +/- 0.4, respectively) than anterior hippocampus (8.0 mmol/L +/- 1.1, 6.0 mmol/L +/- 1.4, 1.5 mmol/L +/- 0.2; P = .005, .02, and .0002, respectively). In the elderly group, mean concentrations were higher in posterior hippocampus (8.6 mmol/L +/- 0.9, 5.6 mmol/L +/- 0.6, 1.5 mmol/L +/- 0.2, respectively) than anterior hippocampus (7.2 mmol/L +/- 1.0, 2.4 mmol/L +/- 0.3, 1.0 mmol/L +/- 0.2; P = .006, .0001, .04, respectively). Mean concentrations were significantly higher in the young group (13.2 mmol/L +/- 1.0, 7.4 mmol/L +/- 0.8, 2.1 mmol/L +/- 0.3, respectively) than in the elderly group (9.0 mmol/L +/- 1.0, 5.8 mmol/L +/- 0.8, 1.8 mmol/L +/- 0.3; P = .0001, .01, .05, respectively). Posteroanterior metabolic gradients differed: NAA decreased faster in the young group (-1.0 mmol/L x cm(-1)) than the elderly group (-0.7 mmol/L x cm(-1)); creatine and choline concentrations decreased faster in the elderly group (-0.8 and -0.058 mmol/L x cm(-1), respectively) than the young group (-0.16 and -0.008 mmol/L x cm(-1), respectively). No left-right metabolic differences were found. CONCLUSION: Significant metabolic heterogeneity was observed between groups and along anteroposterior axis of healthy hippocampus in both groups. Age matching and consistent voxel placement are important for correct comparisons of both absolute metabolic levels and metabolite ratios in longitudinal intra- and intersubject cross-sectional studies.
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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) | 0.001 | 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".