Neonatal testosterone treatment affects the paw elevation of the Mongolian gerbil (Meriones unguiculatus)

Abstract

<p> The present thesis reports an experiment that investigated the phenomenon of asymmetric paw elevation in the tripedal stance of the Mongolian gerbil, and tested the Geschwind-Galaburda extra-genetic theory of human handedness. Neonate gerbils of both sexes were injected with testosterone propionate during the "critical" period of brain development. They were then assessed for asymmetry in eye opening, for anogenital distance, and for paw elevation and scent marking before and after puberty. Eye opening asymmetry was not affected by treatment. Paw elevation was affected by treatment, with treated gerbils of both sexes displaying more right elevations before and after puberty than untreated gerbils. Control females displayed systematic patterns in paw elevation before and after puberty. Adult gerbils in all conditions displayed more consistency in paw elevation than young gerbils. Anogenital distance was increased with treatment, but only in the females. Adult scent marking behavior was marginally reduced with treatment, but only in the males. Results are interpreted within the Geschwind-Galaburda theory of handedness, and the hormonal basis of paw elevation is discussed. </p>