AUTHOR=Miura Momoko , Aoki Naoya , Yamaguchi Shinji , Homma Koichi J. , Matsushima Toshiya 

TITLE=Thyroid Hormone Sensitizes the Imprinting-Associated Induction of Biological Motion Preference in Domestic Chicks

JOURNAL=Frontiers in Physiology

VOLUME=Volume 9 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.01740

DOI=10.3389/fphys.2018.01740

ISSN=1664-042X

ABSTRACT=Filial imprinting is associated with induction of predisposed preference to animations that bear visual features of Johansson’s biological motion (BM), and the induction is limited to a few days after hatching. As thyroid hormone (3,5,3'-triiodothyronine, T3) plays a critical role in determining the sensitive period of imprinting, we examined if exogenously applied T3 (or iopanoic acid, IOP; a selective inhibitor for converting enzymes) could also sensitize (or desensitize) the BM induction. Chicks were trained by using a non-BM stimulus (rotating red toy) for 2 hours according to a conventional imprinting procedure. Thirty min later, trained chicks were tested for preference to a point-light BM animation (walking chick) over a non-BM animation (linear motion; namely BM score), and for the preference for the familiarized stimulus (red toy) over an unfamiliar one (yellow toy; namely imprinting score). In 1-day chicks, those injected with IOP showed significantly lower scores than controls on both BM and imprinting tests. In 4-days chicks, those injected with T3 showed higher scores than control, but the difference in BM score was not significant. When data from these 4 groups were merged, effect of the interaction (T3 x imprinting score) proved to contribute significantly to the BM score. Imprinting and the accompanying T3 surge may be necessary for the predisposed BM preference to appear in 1-day chicks. Even after the conventional sensitive period is over, exogenous T3 can re-sensitize the BM preference as it does imprinting.