Corticothalamic projections from layer 5 of the vibrissal barrel cortex in the rat
Bibliographic record
Abstract
This study bears on the projections of layer 5 cells of the vibrissal sensory cortex to the somatosensory thalamus in rats. Small groups of cells were labeled with biotinylated dextran amine (BDA), and their axonal arborizations were individually reconstructed from horizontal sections counterstained for cytochrome oxidase. Results show that the vast majority ( approximately 95%) of layer 5 axons that innervate the somatosensory thalamus are collaterals of corticofugal fibers that project to the brainstem. The anterior pretectal nucleus, the deep layers of the superior colliculus, and the pontine nuclei are among the structures most often coinnervated. In the thalamus, layer 5 axons terminate exclusively in the dorsal part of the posterior group (Po), where they form clusters of large terminations. Because dorsal Po projects to multiple cortical areas, we sought to determine whether all recipient areas return a layer 5 projection to this part of the thalamus. Additional experiments using fluoro-gold and BDA injections provided evidence that the primary somatosensory area is the sole source of layer 5 projections to dorsal Po but that this thalamic region receives convergent layer 6 projections from the primary and second somatosensory areas and from the motor and insular cortices. These results show that layer 5 projections do not overlap in associative thalamic nuclei, thus defining area-related subdivisions. Furthermore, the coinnervation of brainstem nuclei by layer 5 CT axons suggests that this pathway conveys to the thalamus a copy of the cortical output aimed at brainstem structures.
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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 | 0.000 |
| 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".