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Horm Behav. 2015 Sep;75:45-54. doi: 10.1016/j.yhbeh.2015.07.022. Epub 2015 Jul 29.

Sex, estradiol, and spatial memory in a food-caching corvid.

Author information

1
Department of Integrative Biology and Physiology, The University of California, Los Angeles, 610 Charles E Young Drive East, Los Angeles, CA 90095, USA. Electronic address: mrensel@ucla.edu.
2
Department of Integrative Biology and Physiology, The University of California, Los Angeles, 610 Charles E Young Drive East, Los Angeles, CA 90095, USA.
3
Department of Integrative Biology and Physiology, The University of California, Los Angeles, 610 Charles E Young Drive East, Los Angeles, CA 90095, USA; Laboratory of Neuroendocrinology, Brain Research Institute, The University of California, Los Angeles, 610 Charles E Young Drive East, Los Angeles, CA 90095, USA; Department of Ecology and Evolutionary Biology, The University of California, Los Angeles, 610 Charles E Young Drive East, Los Angeles, CA 90095, USA.

Abstract

Estrogens significantly impact spatial memory function in mammalian species. Songbirds express the estrogen synthetic enzyme aromatase at relatively high levels in the hippocampus and there is evidence from zebra finches that estrogens facilitate performance on spatial learning and/or memory tasks. It is unknown, however, whether estrogens influence hippocampal function in songbirds that naturally exhibit memory-intensive behaviors, such as cache recovery observed in many corvid species. To address this question, we examined the impact of estradiol on spatial memory in non-breeding Western scrub-jays, a species that routinely participates in food caching and retrieval in nature and in captivity. We also asked if there were sex differences in performance or responses to estradiol. Utilizing a combination of an aromatase inhibitor, fadrozole, with estradiol implants, we found that while overall cache recovery rates were unaffected by estradiol, several other indices of spatial memory, including searching efficiency and efficiency to retrieve the first item, were impaired in the presence of estradiol. In addition, males and females differed in some performance measures, although these differences appeared to be a consequence of the nature of the task as neither sex consistently out-performed the other. Overall, our data suggest that a sustained estradiol elevation in a food-caching bird impairs some, but not all, aspects of spatial memory on an innate behavioral task, at times in a sex-specific manner.

KEYWORDS:

Aromatase; Estradiol; Food caching; Scrub-jay; Spatial memory

PMID:
26232613
PMCID:
PMC4648678
DOI:
10.1016/j.yhbeh.2015.07.022
[Indexed for MEDLINE]
Free PMC Article

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