P4–118: Neuroanatomical specificity of psychosis, delusions and hallucinations in Alzheimer's disease
Bibliographic record
Abstract
Psychotic symptoms have a major impact on Alzheimer's disease (AD) and have been associated with faster cognitive decline, caregiver burden and institutionalization. Thus far neuroimaging studies (total number of studies=19) of the neural basis of psychotic symptoms in AD have produced inconsistent results. This inconsistency may in part be explained by differences in the symptoms being studied-while some studies have investigated psychosis as a single entity, others have focused on delusions or hallucinations in isolation. In previous studies, 3 different types of contrast have been employed: 1) psychosis vs no psychosis - PnP 2) delusions vs no delusions - DnD 3) hallucinations vs no hallucinations - HnH. The objective of the present study was to test whether the independent variable definition might explain results heterogeneity. More specifically the objective was to verify whether these different contrasts (PnP, DnD, HnH) produce different cortical correlates of psychosis in a large sample of mild AD. Subjects were all mild AD from the Alzheimer's Disease Neuroimaging Initiative. Delusions and hallucinations were assessed at study entry with the Neuropsychiatric Inventory - caregiver version. Psychosis was defined as the presence of delusions and/or hallucinations. The neuropsychiatric status of control subjects was verified at the 12-month follow-up visit to validate the absence of psychosis, delusions and hallucinations. Using advanced morphometric techniques, three sets of statistical surface maps were generated, one for each of the possible contrast (PnP, DnD, HnH) and compared. The different contrasts were associated with different patterns of cortical atrophy. Delusions were associated with a large area of atrophy of the anterior portion of the left dorsolateral prefrontal cortex. Psychosis was associated with similar although smaller areas of atrophy. Hallucinations were associated with right ventromedial/anterior cingulate and left anterior cingulate atrophy, but with relative preservation of areas of bilateral parietal and occipital cortices. In this study, psychosis, delusions and hallucinations in subjects with mild AD were associated with different patterns of cortical atrophy. This study suggests that a more specific characterization of psychosis may be critical to identify its underlying neuronal circuits.
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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 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".