Effects of gonadectomy in infancy and adulthood on handedness in male and female Mongolian gerbils.

Abstract

When assuming a species-typical tripodal posture, female Mongolian gerbils most often rest on their left forepaws and hold their right forelimbs aloft; male gerbils most often do the reverse. This experiment examined effects of gonadectomy, both in infancy and in adulthood, on the sexually dimorphic asymmetry in forelimb use by Mongolian gerbils when maintaining a tripodal stance. In adulthood, both male and female gerbils that had been gonadectomized at birth reversed their forelimb use while in a tripodal stance: Gonadectomized males used their forelimbs as did sham-operated females, and gonadectomized females used their forelimbs as did sham-operated males. Gonadectomy in adulthood abolished the sexual dimorphism in forelimb use seen in sham-operated subjects. It was concluded that gonadal hormones have organizational as well as possible activational effects on adult patterns of forelimb use by gerbils.

Testosterone and grasp-reflex differences in human neonates

“…Accordingly, the neonatal T measured in the present work may be involved in the organisational effects that we were looking for. Clark, Santamaria, Robertson, and Galef (1998) have provided strong evidence of organisational effects and weaker evidence of activational effects of gonadal hormones on lateral asymmetries in forelimb use by Mongolian gerbils.…”