Insular Cortical Thickness Distinguishes Subjective Cognitive Decline from Normal Cognitive Aging
Bibliographic record
Abstract
BACKGROUND: Subjective cognitive decline (SCD), marked by memory concerns despite normal objective cognition, is considered an at-risk group for Alzheimer's disease (AD), but SCD due to AD is challenging to identify due to lack of objective biomarkers. This study examined group differences in cognitive performance and brain structures typically affected in AD between SCD and cognitively unimpaired (CU) older adults, and explored associations between cognition and brain structure within groups. METHOD: Participants included 34 SCD [17F, mean age=70.9 (5.62) years] and 26 CU [16F, mean age 71.4 (7.25) years], classified based on presence or absence of memory concerns, clinical assessment, and normal neuropsychological (NP) performance. Cognitive performance was assessed using a modified Preclinical Alzheimer's Cognitive Composite (PACC). Structural MRI was acquired at 3T using MPRAGE. Regions-of-interest (ROIs) included medial temporal lobe regions, anterior and posterior cingulate, insula, and precuneus. Group differences in ROIs and PACC were tested using ANCOVA, covarying for age, sex and education. Pearson's r was used to assess relationships between PACC scores and ROIs which differed amongst groups. Benjamini-Hochberg was used to correct for multiple comparisons in all analyses. RESULT: Relative to CU, SCD participants scored lower on the PACC (F(1, 55) = 11.12, p = 0.00156), which remained significant after correction for multiple comparisons. Amongst ROIs, only the left insula showed a group difference, with reduced cortical thickness in SCD compared to CU (F(1, 55) = 4.81, p = 0.0302). Left insular cortical thickness was positively correlated with PACC scores (r = 0.34, p = 0.0469) in the SCD group. However, neither finding involving the left insula remained significant after Benjamini-Hochberg correction. No association between PACC and the left insula was observed in the CU group. CONCLUSION: Despite normal neuropsychological test performance, individuals with SCD show lower PACC scores and reduction of left insular cortical thickness. The involvement of the insula in SCD is compatible with the higher prevalence of anxiety and depression symptoms in SCD reported in the literature. These findings require replication using larger sample sizes and AD-related neuropathologic markers to support the potential utility of insular cortical atrophy as a biomarker for SCD due to AD.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".