The amnesic effects of propofol on functional connectivity in the hippocampus determined by functional magnetic resonance imaging in volunteers
Bibliographic record
Abstract
BACKGROUND: One of the primary actions of general anaesthetic agents, apart from inducing a state of unconsciousness, is reversible impairment of memory formation during the period of administration. Failure to induce and maintain amnesia can result in recall of accidental intraoperative awareness and contribute to adverse psychological health outcomes. The precise mechanisms of action by which general anaesthetics achieve their amnesic effects are not fully understood. To this end, we focused on the hippocampus, a region critical for the formation of new episodic explicit long-term memories of the type normally inhibited by general anaesthetics. METHODS: We enrolled 25 healthy adult volunteers who underwent functional magnetic resonance neuroimaging (fMRI) whilst sedated with a plasma target-controlled infusion of the anaesthetic agent propofol. The functional connectivity (synchronised neuronal activity with other brain regions) of the hippocampus and microanatomical hippocampal subregions was assessed at baseline, under sedation, and during recovery. Serial plasma propofol concentrations and responses to an auditory stimulus semantic decision task were measured. Post-scanning memory testing was conducted, and memory performance was related to the fMRI data. RESULTS: Functional connectivity changes associated with an amnesic but subhypnotic depth of propofol sedation were predominantly characterised by a reduced connectivity signature of the hippocampus stratum radiatum, stratum lacunosum, stratum moleculare, CA1 stratum pyramidalis, and CA4/dentate gyrus subfields with the precuneus. CONCLUSIONS: We provide evidence for differential actions of propofol on hippocampal subdivisions and limbic circuits related to amnesic efficacy, which suggests a more significant role of the precuneus in long-term memory consolidation than previously thought.
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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 | 0.000 | 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".