Viral Tracing Identifies Parallel Disynaptic Pathways to the Hippocampus
Bibliographic record
Abstract
Electrophysiological and lesion studies in rodents have shown that the dorsal (septal) and ventral (temporal) segments of the hippocampus have functional specializations that can be understood in terms of their anatomical connections with distinct brain areas. Here we explore the circuitry associated with the hippocampus using the pseudorabies virus-Bartha strain (PRV-Bartha) tracer in the rat to examine both direct (first-order) and indirect (second-order) projections to the hippocampus. Based on analysis of PRV-Bartha infection density, we demonstrate two parallel pathways from the limbic cortex to the hippocampus. A dorsal "spatial cognition" pathway provides disynaptic input from the retrosplenial, anterior cingulate, and orbital cortex to the dorsal hippocampus, with potential synaptic relays in the anterior thalamic nuclei and dorsolateral entorhinal cortex. A ventral "executive control" pathway provides disynaptic input from the prelimbic, infralimbic, and orbital cortex to the ventral hippocampus, with potential synaptic relays in the midline thalamic nuclei and the rostral caudomedial entorhinal cortex. These data suggest a new anatomical framework for understanding the functional interactions between the cortex and hippocampus, especially in cognitive disorders that involve both structures, such as frontotemporal dementia.
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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 | 0.000 |
| 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 | 0.000 | 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".