Unveiling a Novel Memory Center in Humans: Neurochemical Identification of the <i>Nucleus Incertus</i> , a Key Pontine Locus Implicated in Stress and Neuropathology
Bibliographic record
Abstract
Abstract Background The nucleus incertus (NI) was originally described by Streeter in 1903, as a midline region in the floor of the fourth ventricle (4V) of the human brain with an ‘unknown’ function. More than a century later, the neuroanatomy of the NI including its forebrain target regions has been described in lower vertebrates, but not in humans. Therefore, we examined the neurochemical anatomy of the human NI using several markers, including the neuropeptide, relaxin-3 (RLN3), and began to explore the distribution of the NI-related RLN3 innervation of the hippocampus. Methods Histochemical staining of serial, coronal sections (30 µm) of control human postmortem pons was conducted to reveal the presence of the NI by detection of immunoreactivity (IR) for the neuronal marker, microtubule-associated protein-2 (MAP2), two markers present in rat NI, glutamic acid dehydrogenase (GAD)-65/67 and corticotrophin releasing hormone receptor 1 (CRHR1), and RLN3, which is highly expressed in a major population of NI neurons in diverse species. RLN3 and vesicular GABA transporter 1 ( vGAT1 ) mRNA was detected by multiplex, fluorescence in situ hybridization. Postmortem pons sections containing the NI from an Alzheimer’s disease (AD) case were immunostained for phosphorylated-tau (AT8 antibody), to explore potential relevance to neurodegenerative diseases. Lastly, sections of human hippocampus were stained to detect RLN3-IR and somatostatin (SST)-IR, as SST is expressed in interneurons targeted by RLN3 projections in rodents. Results In the dorsal, anterior-medial region of the human pons, neurons containing RLN3– and MAP2-IR, and RLN3/vGAT1 mRNA-positive neurons were observed in an anatomical pattern consistent with that of the NI in other species. GAD65/67– and CRHR1-immunopositive neurons were also detected within this area. Furthermore, RLN3– and AT8-IR were co-localized within NI neurons of an AD subject. Lastly, RLN3-IR was detected in neurons within the CA1, CA2, CA3, and DG areas of the hippocampus, in the absence of RLN3 mRNA. In the DG, RLN3– and SST-IR were co-localized in a small population of neurons. Conclusions Aspects of the anatomy of the human NI are shared across species, including a population of RLN3-expressing neurons and a RLN3 innervation of the hippocampus. Accumulation of phosphorylated-tau in the NI suggests its possible involvement in AD pathology. Further characterization of the neurochemistry of the human NI will increase our understanding of its functional role in health and disease. Graphical Abstract Created with BioRender.com
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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".