Neural, not gonadal, origin of brain sex differences in a gynandromorphic finch.
Level 5 - mechanism / opinion, no new human data
Animal study / single-specimen laboratory case report
PubMed 12672961 · doi:10.1073/pnas.0636925100
What was done
Investigators analyzed the neural phenotype of the brain in a rare gynandromorphic finch whose right hemisphere was genetically male and left hemisphere was genetically female, sharing a single common gonadal hormone environment.
What was found
The neural song circuit on the genetically male right side exhibited a more masculine phenotype than the genetically female left side. Both sides of the song circuit were more masculine than those of typical female finches. The abstract reports no numerical measurements or statistical values.
Why it matters
This study provides evidence that intrinsic genetic sex of brain cells directly influences neural sexual differentiation independently of circulating gonadal hormones.
Limits
The study is a single-subject natural experiment (n = 1) in a non-mammalian avian model. The abstract provides no quantitative morphometric or hormonal measurements, and findings cannot be directly extrapolated to human neurobiology.
Cited by
- supports In gynandromorphic songbirds, the brain region HVC is larger on the genetically male side of the brain than on the female side.