A combined physiological, psychophysical, and functional neuroimaging study of rectal function in patients with irritable bowel syndrome
Bibliographic record
Abstract
Introduction and aims. A key feature of irritable bowel syndrome (IBS) is rectal hypersensitivity exemplified by a reduced pain threshold to rectal stimuli. However, it is contentious whether abnormalities in rectal motor physiology and/or the activity of specific brain regions contribute to IBS symptomology. To gain insight into the underlying peripheral and/or central dysfunction in IBS, the aim of this thesis was to determine whether IBS patients have abnormal rectal, psychophysical or brain responses to low (urge producing) or high (pain producing) rectal pressures. Methods. IBS patients and healthy control subjects were assessed in two sessions. The first session assessed rectal physiology and psychophysical responses during: (a) ascending stepwise distensions terminating upon report of moderate pain, (b) phasic or (c) tonic distensions at a single pressure eliciting moderate urge or moderate pain intensity. Qualities of the pain experience during single pressure distensions were assessed with the McGill Pain Questionnaire (MPQ). In the second session, participants underwent percept-related functional magnetic resonance imaging (fMRI) evoked by rectal pressure distensions eliciting either moderate urge or moderate pain intensity. Results. Rectal physiology abnormalities in IBS included a lower volume-pressure ratio during phasic single-pressure distensions and a slower rate of rectal relaxation during urge- versus pain-eliciting tonic distensions. Psychophysical abnormalities in IBS included an altered relationship between the three rectal distension-evoked percepts of urge, unpleasantness and pain, the lingering of distension-evoked percepts, and higher scores on the affective/evaluative dimension of the MPQ evoked by painful rectal distension. Percept-related fMRI revealed that IBS patients, but not controls had rectal-evoked activation of primary somatosensory cortex during low-pressure distension, and medial thalamus and hippocampus during painful distension. However, activations in rostral anterior cingulate cortex and dorsal right anterior insula during low- and high-pressure distension were present in the control group but not IBS group. Conclusions. This thesis demonstrated abnormal rectal and psychophysical responses to distension in IBS. Furthermore, abnormal brain responses in IBS may reflect rectal hypersensitivity, abnormal processing of attentional and affective aspects of pain, and abnormal interoception and/or visceromotor integration.
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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 | 0.000 |
| 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".