Distinct patterns of posterior default mode network‐medial temporal lobe connectivity in mild cognitive impairment and subjective cognitive decline
Bibliographic record
Abstract
Abstract Background Older adults with subjective cognitive decline (SCD) show alterations in functional connectivity of the posterior default mode network (DMN), but both increases and decreases have been reported, suggesting that changes in connectivity may be nonlinear across the AD spectrum. Alternatively, the variable findings may be attributable to heterogeneity within SCD samples. Specifically, studies of SCD exclude individuals with current depression, but history of past remitted depression is not typically ascertained. This is problematic because emerging evidence suggests that state‐independent aberrations in neural networks, including within posterior DMN, persist following recovery from depression. In the current study, we compared posterior DMN connectivity using resting state functional magnetic resonance imaging (rs‐fMRI) amongst SCD, mild cognitive impairment (MCI) or cognitively unimpaired (CU) older adults free of current or remitted depression. Method Participants were 58 older adults who were screened via psychiatric/medical assessment for current or past history of depression and neurological conditions, and consisted of 21 SCD [12F, mean age 70.6(SD5.5)] defined as perception of memory decline with concern or worry and normal neuropsychological (NP) test scores, 12 MCI [4F, mean age 73(SD6.8)] defined as subjective cognitive complaints with functional independence and impaired performance on >=2 NP tests, and 25 CU [15F, mean age 71.8(SD7.2)] based on normal NP scores and absence of subjective memory decline with worry. Rs‐fMRI was acquired using gradient‐echo EPI BOLD at 3T and processed using CONN toolbox. Seed analysis using a posterior cingulate cortex (PCC) seed (x=‐6, y=‐52, z=40) was performed. Hippocampus and parahippocampal gyrus were target regions‐of‐interest. Multivariate ANOVA was used to examine group differences in PCC connectivity followed by post hoc comparisons using Dunnett’s test. Result Groups differed in PCC connectivity with the right hippocampus [F(2, 55)=3.74, P=.03] and left posterior parahippocampal gyrus [F(2, 55)=3.35, P=.042]. Relative to CU, PCC‐right hippocampal connectivity was reduced in MCI (P=.028), while PCC‐left parahippocampal connectivity was found in SCD (P=.024). Conclusion Disruptions in posterior DMN connectivity were observed in SCD and MCI that were not attributable to current or remitted depression. The distinct patterns of posterior DMN disruption are consistent with putative non‐linear changes in neural network connectivity with AD progression.
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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 | 0.000 | 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) | 0.001 | 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".