Morphology of parietal sulci: Intraparietal sulcus, anterior intermediate parietal sulcus of Jensen, and postcentral sulcus with its relation to somatic sensory representations
Bibliographic record
Abstract
A comprehensive study of the functional organization of the parietal cortex in the human brain requires a clear understanding of the sulcal-gyral morphology and its variability in individual cerebral hemispheres. In the studies presented in this thesis, the Magnetic Resonance Imaging (MRI) technique is used to advance our knowledge of the morphology of several main parietal sulci, namely the postcentral sulcus, the transverse postcentral sulcus, the intraparietal sulcus, and the anterior intermediate parietal sulcus of Jensen (the sulcus of Jensen) by studying the sulci along their entire course in three planes of section: coronal, horizontal and sagittal. This approach provides critical information concerning the association between the end-points of the neighbouring sulci from the surface of the brain to the fundus and subdivision of the major sulci into basic anatomical units for the study of cortical folding patterns.The first study of this thesis is a morphological examination of the region of the anterior parietal lobe in a large sample of MRI brain scans. The anterior parietal lobe is composed of the somatosensory cortex on the postcentral gyrus and it is bounded posteriorly by the postcentral sulcus. The results demonstrate that the postcentral sulcus is a complex of distinct segments, which extend from the medial edge of the hemisphere to the lateral fissure. In certain hemispheres, the postcentral sulcus merges with a prominent sulcus of the posterior parietal lobe, the intraparietal sulcus, on the surface of the brain, but the sulci are always separated by a small gyral passage in the depth. Another sulcus, the transverse postcentral sulcus, extends in parallel with the postcentral sulcus on the ventral part of the postcentral gyrus. The transverse postcentral sulcus may be considered an inferior part of the postcentral sulcal complex because its presence in the brain coincides with an overall shorter length of the postcentral sulcus and, in some cases, it overlaps with the ventral end of the postcentral sulcus.The second study examines the intraparietal sulcus and a sulcus closely associated with it, namely the sulcus of Jensen in many MRI brain volumes. The cortex of the intraparietal sulcus is implicated consistently in studies of visual-motor coordinate transformations, visual-spatial attention, and visual guidance of movement in space. The findings demonstrate that, most frequently, the intraparietal sulcus may be divided into two branches, the anterior and posterior rami, by a gyral bridge, submerged or visible from the surface of the brain. The sulcus of Jensen is located close to this gyral bridge between the two rami of the intraparietal sulcus and it forms a number of patterns with the intraparietal sulcus, most frequently occurring as a side-branch of the intraparietal sulcus or a shallow sulcus associated with it. Commonly, the ventral termination of the sulcus of Jensen is located between the first and second caudal branches of the superior temporal sulcus, which terminate in the inferior parietal lobe, but in a small number of hemispheres it may merge superficially with the first caudal branch of the superior temporal sulcus.The third study applies the morphological findings from the first study to demonstrate a relationship between the structure of the postcentral sulcus and the sensorimotor representations of different body parts in the anterior parietal lobe. The findings demonstrated that the posterior border of the sensorimotor representation of a specific body part was formed by a specific segment of the postcentral sulcus. In addition, the transverse postcentral sulcus functionally related to the sensorimotor representations of the mouth and tongue on the postcentral gyrus in the hemispheres in which it was present. Thus, the morphology of the anterior parietal lobe relates strongly to the functional sensorimotor activation patterns.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".