Default Mode Network Segregation Decreases in Healthy Brain Aging
Bibliographic record
Abstract
The default mode network (DMN) constitutes a cluster of interconnected brain regions engaged in internal cognitive processes, such as interoception, memory recall, and self-referential thinking. The DMN is a task-negative network, displaying increased activity during rest but reduced activity during cognitive tasks. Resting-state functional magnetic resonance imaging (rs-MRI) examines this task-negative nature by tracking low-frequency fluctuations in the blood oxygenation level-dependent signal as an indirect marker for changes in brain activity. Many cross-sectional studies have focused on understanding DMN organization in healthy brain aging, however, these studies fail to account for intra-individual variance. To address this limitation, we conducted a longitudinal, pilot analysis that investigated changes in DMN segregation index ($SI$), simply defined as the ratio of within-network connectivity relative to between-network connectivity, across the healthy adult lifespan. Specifically, a subset of the Calgary Normative Study data (67 healthy individuals scanned twice over an interval of 3.1 ± 0.3 years, mean ± standard deviation) was analyzed. A linear mixed effects model was used to examine the effects of $Age,Age^{2}$, and Sex, as well as Age $\times$ Sex interactions on DMN SI. We observed a significant decline in DMN $SI$ with $\operatorname{Age}^{2}(t_{128}=-2.79,\ p\leq 0.001)$. Males demonstrated reduced DMN segregation compared to females $(t_{126}=-2.53,p=0.01$). By identifying this decline in DMN $SI$, our study advances the understanding of age-and sex-associated changes in the DMN architecture, laying the groundwork for future work. In conclusion, our study confirms the significance of changes in the DMN in healthy brain aging using longitudinal analysis. Using the $SI$ metric strengthened our investigation by combining within- and between-network connectivity into a more robust metric that reflects complex and dynamic brain changes.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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 | 0.000 | 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".