Mild behavioral impairment as an indicator of early dementia neurodegeneration: Evidence from structural neuroimaging
Bibliographic record
Abstract
Abstract Background Mild behavioral impairment (MBI) refers to the de novo emergence of persistent neuropsychiatric symptoms in older adults and has been associated with cognitive decline and incident dementia. The purpose of this study was to identify the structural neural correlates of MBI using a hypothesis‐driven region‐of‐interest (ROI) approach. Method The study cohort consisted of 744 participants (60.3% female; mean and SD of age = 71.0 ± 9.7 years; mean and SD of education: 15.8 ± 5.3 years) without dementia from the National Alzheimer’s Coordinating Centre dataset. Structural T1‐weighted images for each participant were processed and segmented using FreeSurfer and then normalized by age, sex, intracranial volume, scanner characteristics, and image quality to generate adjusted measures of grey matter volume (GMV) for each ROI. Our primary ROIs included five regions, each representing one Braak stage: entorhinal cortex (stage I), hippocampus (stage II), fusiform gyrus (stage III), inferior temporal cortex (stage IV), and frontal pole (stage V). We also included three hippocampal subfields (CA1, CA3, CA4) and four ROIs commonly associated with various psychiatric disorders (amygdala, insula, anterior cingulate, prefrontal cortex) as a secondary analysis. All ROIs are anatomically highlighted in Figure 1. Participants were classified as MBI+ if they presented with MBI symptoms derived from the Neuropsychiatric Inventory Questionnaire for two consecutive visits one year apart. Logistic regressions adjusting for cognitive diagnosis (cognitively normal, n = 568; mild cognitive impairment, n = 176) were used to model the relationship between ROI GMV (predictor) and MBI status (outcome). Result As shown in Table 1, lower GMV in early Braak stage ROIs (entorhinal cortex and hippocampus) was associated with MBI+ status. This trend was maintained for all hippocampal subfield ROIs. However, mid‐late Braak stage ROI (fusiform gyrus, inferior temporal cortex, frontal pole) GMVs were not associated with MBI status. For psychiatric disorder ROIs, lower GMV in only the amygdala was associated with MBI+ status. Conclusion Our findings demonstrate that the presence of MBI may implicate neurodegeneration in regions linked to early‐stage dementia. Furthermore, this explicitly identifies MBI as a neurodegenerative marker sharing few neuroanatomical correlates with psychiatric disorders, despite their clinical manifestations. aging after age 90.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.009 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".