Perinatal gonadal hormones significantly affect subsequent sex differences
in reproductive and non-reproductive behaviors in rodents. However, the inf
luence of the sex chromosomes on these behaviors has been largely ignored.
To assess the influence of the non-pseudoautosomal region of the Y chromoso
me, C57BL/JEi male and female mice and mice from the C57BL/6JEi-Y-POS conso
mic strain were given behavioral tests known to distinguish males from fema
les. The C57BL/6JEi-YPOS strain contains sex-reversed XY-females which, whe
n compared to their XX-female siblings, allow assessment of the influence o
f the Y chromosome in a female phenotype. XX-females and XY-females did not
differ on open-field activity, the Lashley maze, or active avoidance learn
ing, but XY-females were significantly better than XX-females on the Morris
hidden platform spatial maze. These findings suggest that males may have b
oth a genetic and a hormonal mechanism to ensure visuospatial superiority.
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