Multiparametric and Multivariate Analysis of White Matter Microstructure and its Relationship with Psychosexuality
Bibliographic record
Abstract
Neuroimaging research on psychosexuality, including gender identity and sexual orientation, often focuses on Western adults and lacks adolescent and non-Western populations. Here, the dissertation addresses these absences by investigating white matter (WM) microstructure, which characterizes the structural connectivity of the brain. WM microstructure has been associated with differences in pubertal development, sex steroid hormones, and psychosexuality. Three multiparametric and multivariate studies investigated developmental, hormonal, and psychosexual associations with WM microstructure in sexually and gender diverse Canadian adolescents and Thai adults. Metrics of WM tissue organization, density, and myelination were derived from diffusion tensor imaging using fractional anisotropy (FA), axial (AD), and radial diffusivity (RD). T1 relaxometry, an additional proxy of myelination was included in Study 1. The studies used whole-brain, mass-univariate tract-based spatial statistics and multivariate partial least squares analyses. Study 1 investigated WM microstructural associations in cisgender and transgender adolescents with age, estradiol, physical development, and sexual attractions. Study 2 compared the WM microstructure of sexually and gender diverse adults, including a group of transfeminine individuals using gender-affirming hormones (GAH). In the same adults, Study 3 explored associations between WM microstructure, psychosexuality, and performance on a mental rotation task (MRT). The findings indicated that pubertal development, hormones, and psychosexuality were related to WM microstructure. Study 1 revealed strong relationships between AD and T1 relaxometry and pubertal development in most WM tracts in cisgender boys. Weaker and less consistent associations were found in cisgender girls and transgender boys. Study 2 replicated Western findings of FA, AD, and RD differences in straight cisgender men and women in the fornix, corpus callosum, and several association tracts, but the indices were not differentiated by androphilic and gynephilic sexual attractions. GAH-use was related to lower organization and faster diffusion in the forceps minor of transfeminine adults. In Study 3, a multiplicity of brain patterns illustrated the relationship between MRT score and WM microstructure and appeared to depend on group membership, suggesting that brain-behaviour associations may vary with psychosexual identity. Together, the studies reveal the complexity of characterizing psychosexual-neural phenotypes. The dissertation concludes with a discussion of potential underlying mechanisms, including culture, genetics, and hormones.
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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 | 0.001 | 0.002 |
| 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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".