Intra and inter‐network connectivity in the olfactory network and default mode network across the Alzheimer's disease spectrum: An analysis of COMPASS‐ND cognitive and imaging data
Bibliographic record
Abstract
BACKGROUND: Olfactory dysfunction is a prevalent and early symptom of Alzheimer's disease (AD), often preceding the core memory impairment features of AD. Moreover, brain regions integral to olfactory processing are implicated in the early AD pathophysiology. Previous work has identified olfactory deficits in individuals with subjective cognitive decline (SCD), the earliest at-risk stage of AD. Few studies, however, have examined the associations between cognitive and olfactory changes, and their neural correlates, in this population. METHOD: Data from the Comprehensive Assessment of Neurodegeneration and Dementia (COMPASS-ND) were used, including resting-state functional MRI and neuropsychological data. Participants included individuals with SCD (n = 128), mild cognitive impairment (MCI; n = 315), AD (n = 116), and cognitively unimpaired older adults (n = 84) who served as controls. We examined group differences and associations between olfactory dysfunction, as measured by the Brief Smell Identification Test, and cognition. Independent components analysis was used to identify the resting-state olfactory network (ON) and default mode network (DMN). We examined intra- and internetwork functional connectivity in the ON and DMN and related these findings to olfactory performance and cognition. RESULT: We observed groupwise deficits in olfactory and cognitive function in MCI and AD groups relative to controls (p < 0.01), but not between SCD and controls (p > 0.05). Poorer olfactory performance in the MCI and SCD groups was related to worse memory (p < 0.05) but not in controls (p > 0.05). We observed increased connectivity within the ON in SCD and decreased connectivity in MCI and AD, relative to controls (p-fdr < 0.05). We expect to find alterations in connectivity within the DMN and between the ON and DMN, which we expect to relate to poorer olfaction and cognitive performance. CONCLUSION: These findings suggest a coupling of olfaction and memory performance in SCD, that is not present in controls, despite similar sensory and cognitive performance. Moreover, we expect these changes will relate to changes in connectivity within and between the ON and DMN. These data contribute to the potential utility of measuring olfactory performance as a non-invasive and reliable biomarker in SCD and MCI for conversion to later stages of the AD continuum.
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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| 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".