Steroid-dependent plasticity in the medial amygdala.
Level 5 - mechanism / opinion, no new human data
Narrative review of animal experimental research
PubMed 16330154 · doi:10.1016/j.neuroscience.2005.06.018
What was done
The author reviewed experimental findings in adult rats and Siberian hamsters investigating how circulating gonadal steroids (androgens and estrogens) and environmental factors (photoperiod and social housing) alter the morphology (soma size and regional volume) of the posterodorsal subnucleus of the medial amygdala (MePD).
What was found
The abstract reports no numerical values. Qualitatively, reversing adult circulating androgen levels reversed sex differences in rat MePD soma size and regional volume. Maintaining a masculine cell size required both androgen and estrogen receptor activation, whereas maintaining volume required only estrogen receptor activation. In Siberian hamsters, winter photoperiod-induced MePD regression was prevented by female co-housing, and testosterone stimulated MePD morphology in castrated males only under summer photoperiods.
Why it matters
These findings show that sexually dimorphic neural structures in rodents retain substantial structural plasticity in adulthood driven by ongoing hormonal and environmental cues, rather than being permanently fixed during neonatal development.
Limits
All reviewed data derive from rodent models (rats and hamsters), precluding direct translation to human brain morphology. The abstract provides narrative conclusions without quantitative effect sizes, sample sizes, or variance estimates.
Cited by
- supports Research by Brad Cooke demonstrated that the sex difference in the medial amygdala in animals disappears within a few weeks following testosterone removal in adult males.