The inferior frontal sulcus in the chimpanzee brain: morphological examination and association with oro-facial communication
Bibliographic record
Abstract
There has been considerable interest in the neuroanatomical homologue of Broca's region in nonhuman primates, particularly in our phylogenetically closest relative the chimpanzee (Pan troglodytes), to further our understanding of the evolution of language in hominins. The inferior frontal sulcus (ifs) is a critical landmark below which lie language production areas in the language-dominant hemisphere of the human brain, and its homologue is found in the chimpanzee brain. The present study examined the variability in the morphology of the ifs in 73 chimpanzee brains (ie 146 hemispheres). Examination was carried out on surface reconstructions derived from in vivo 3 T magnetic resonance imaging scans, which permitted detailed intra-sulcal assessment. Based on the connections formed by the ifs and adjacent sulci, two frequent and three less frequent morphological types were identified. The average location and spatial variability of the ifs were quantified in the form of spatial surface probability maps. Relationships were also established between specific morphological features of the ifs in the left hemisphere and oro-facial communication abilities, as measured by attention-getting sound production. These findings refine our knowledge of prefrontal sulcal organization in hominids and offer valuable insights into the structural blueprints that supported the emergence of speech in humans.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".