Estimating Psychosis Risk in Individuals at Clinical High Risk using Event–related Brain Potential Indices of Cognitive Processing
Bibliographic record
Abstract
Background: The N400 event-related brain potential waveform occurs in response to potentially meaningful stimuli and this effect is thought to reflect greater activation of related versus unrelated concepts in long-term semantic memory. In normal participants, related targets elicit smaller (less negative) N400 amplitudes than do unrelated items. These N400 semantic priming effects are found to be attenuated in schizophrenia patients, suggesting impaired activation of related concepts. Individuals at clinical high risk (CHR) for schizophrenia experience subthreshold symptoms of the disorder, including decreased functioning. The event-related potential Mismatch Negativity (MMN), P3a and gamma ASSR measures have been found to be abnormal in CHR patients compared to controls.Aim: We aimed to examine whether N400 semantic priming deficits are a biomarker of the CHR state, whether decreased N400 semantic priming predicts conversion to psychosis in this population over two years, and whether N400 effects predict high-risk symptomatology and impaired functioning over time. Methods: We examined the N400 ERP semantic priming effect, the MMN, P3a and gamma ASSR in a sample of CHR participants and healthy controls. We then re-assessed the CHR group at one and two years to measure global functioning, positive psychotic symptoms, and conversion status. Results: We found a deficient N400 effect in the CHR group compared to controls. In this group, the N400 was related to role functioning and cognitive defects at baseline, social functioning at one-year follow-up, and improvement of positive symptoms and functioning over two years’ follow-up. Conclusion: This study indicates that the N400 priming effect is deficient at the CHR state and may contribute to the worsening of positive symptoms and functioning over time. Given that only a minority of CHR individuals will go on to develop schizophrenia, efforts to refine our ability to identify those at highest risk are critical. These findings may help to target limited resources to those individuals at risk who need it the most and minimize unnecessary treatment and side effects.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".