Abstract
It is widely assumed that chronic stress and corresponding chronic elevations of glucocorticoid levels have deleterious effects on animals' brain functions such as learning and memory. Some animals, however, appear to maintain moderately elevated levels of glucocorticoids over long periods of time under natural energetically demanding conditions, and it is not clear whether such chronic but moderate elevations may be adaptive. I implanted wild-caught food-caching mountain chickadees (Poecile gambeli), which rely at least in part on spatial memory to find their caches, with 90-day continuous time-release corticosterone pellets designed to approximately double the baseline corticosterone levels. Corticosterone-implanted birds cached and consumed significantly more food and showed more efficient cache recovery and superior spatial memory performance compared with placebo-implanted birds. Thus, contrary to prevailing assumptions, long-term moderate elevations of corticosterone appear to enhance spatial memory in food-caching mountain chickadees. These results suggest that moderate chronic elevation of corticosterone may serve as an adaptation to unpredictable environments by facilitating feeding and food-caching behaviour and by improving cache-retrieval efficiency in food-caching birds.
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Selected References
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- Diamond D. M., Bennett M. C., Fleshner M., Rose G. M. Inverted-U relationship between the level of peripheral corticosterone and the magnitude of hippocampal primed burst potentiation. Hippocampus. 1992 Oct;2(4):421–430. doi: 10.1002/hipo.450020409. [DOI] [PubMed] [Google Scholar]
- Harvey S., Phillips J. G., Rees A., Hall T. R. Stress and adrenal function. J Exp Zool. 1984 Dec;232(3):633–645. doi: 10.1002/jez.1402320332. [DOI] [PubMed] [Google Scholar]
- Lynn Sharon E., Breuner Creagh W., Wingfield John C. Short-term fasting affects locomotor activity, corticosterone, and corticosterone binding globulin in a migratory songbird. Horm Behav. 2003 Jan;43(1):150–157. doi: 10.1016/s0018-506x(02)00023-5. [DOI] [PubMed] [Google Scholar]
- McEwen B. S., Sapolsky R. M. Stress and cognitive function. Curr Opin Neurobiol. 1995 Apr;5(2):205–216. doi: 10.1016/0959-4388(95)80028-x. [DOI] [PubMed] [Google Scholar]
- McEwen B. S. The neurobiology of stress: from serendipity to clinical relevance. Brain Res. 2000 Dec 15;886(1-2):172–189. doi: 10.1016/s0006-8993(00)02950-4. [DOI] [PubMed] [Google Scholar]
- Pravosudov V. V., Clayton N. S. Effects of demanding foraging conditions on cache retrival accuracy in food-caching mountain chickadees (Poecile gambeli). Proc Biol Sci. 2001 Feb 22;268(1465):363–368. doi: 10.1098/rspb.2000.1401. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pravosudov V. V., Kitaysky A. S., Wingfield J. C., Clayton N. S. Long-term unpredictable foraging conditions and physiological stress response in mountain chickadees (Poecile gambeli). Gen Comp Endocrinol. 2001 Sep;123(3):324–331. doi: 10.1006/gcen.2001.7684. [DOI] [PubMed] [Google Scholar]
- Pravosudov Vladimir V., Clayton Nicola S. A test of the adaptive specialization hypothesis: population differences in caching, memory, and the hippocampus in black-capped chickadees (Poecile atricapilla). Behav Neurosci. 2002 Aug;116(4):515–522. [PubMed] [Google Scholar]
- Pravosudov Vladimir V., Kitaysky Alexander S., Saldanha Colin J., Wingfield John C., Clayton Nicola S. The effect of photoperiod on adrenocortical stress response in mountain chickadees (Poecile gambeli). Gen Comp Endocrinol. 2002 Apr;126(2):242–248. doi: 10.1006/gcen.2002.7798. [DOI] [PubMed] [Google Scholar]
- Pravosudov Vladimir V., Mendoza Sally P., Clayton Nicola S. The relationship between dominance, corticosterone, memory, and food caching in mountain chickadees (Poecile gambeli). Horm Behav. 2003 Aug;44(2):93–102. doi: 10.1016/s0018-506x(03)00119-3. [DOI] [PubMed] [Google Scholar]
- Saldanha C. J., Schlinger B. A., Clayton N. S. Rapid effects of corticosterone on cache recovery in mountain chickadees (Parus gambeli). Horm Behav. 2000 Mar;37(2):109–115. doi: 10.1006/hbeh.2000.1571. [DOI] [PubMed] [Google Scholar]
- Sapolsky R. M. Why stress is bad for your brain. Science. 1996 Aug 9;273(5276):749–750. doi: 10.1126/science.273.5276.749. [DOI] [PubMed] [Google Scholar]