Females have a larger hippocampus than males in the brood-parasitic brown-headed cowbird.

Sherry, David F.; Forbes, Mark R.; Khurgel, Moshe; Ivy, Gwen O.

doi:10.1073/pnas.90.16.7839

Cited by 180 publications

(139 citation statements)

References 32 publications

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“…It is important to acknowledge that, unlike studies in the eastern brown-headed cowbird (M. a. ater; Sherry et al, 1993), our study and two others (Uyehara, 1994; Uyehara & Nairns, 1992) that examined the western subspecies (M. a. obscurus) did not find that WCF had a significantly larger Hp than WCM. These discrepancies could result from methodological differences.…”

Section: Cowbird Population Differencescontrasting

confidence: 91%

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Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Day

Guerra²,

Schlinger³

et al. 2008

Behavioral Neuroscience

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In brood parasitic cowbirds, hippocampus (Hp) size is correlated with environmental spatial memory demands. Searching for host nests is the presumed causal factor influencing cowbird Hp size, because Hp volumes vary across species, sexes, and seasons according to nest-searching participation. Brownheaded cowbirds have female-only nest searching and, at least in the eastern subspecies, a larger Hp in females than in males, suggesting that nest searching influences cowbird Hp size. We predicted that female brown-headed cowbirds housed in aviaries lacking host nests would have a smaller Hp than wild-caught females whereas males would be unaffected. We found that the Hp was smaller in captive females, but not males, compared to their wild-caught counterparts. This did not appear to be due to general effects of an impoverished environment on all brain regions. Our results imply that interruption of nest searching in cowbirds prevents seasonal increase in Hp size in females. Future studies should isolate which behavioral differences between wild and captive birds contributed to captivity-induced changes in Hp volume in females while not affecting males. Keywordscowbird; hippocampus; sex differences; brain plasticity; brood parasitism Variation in environmental spatial demands is related to variation in hippocampus (Hp) size among closely related species, between sexes, and across seasons in mammalian, avian, and reptilian species. For example, food-storing behaviors in birds (Clayton, 1995a;Hampton, Sherry, Shettleworth, Kurgel, & Ivy, 1995;Hampton & Shettleworth, 1996;Healy & Krebs, 1992;Krebs, Sherry, Healy, Perry, & Vaccarion, 1989;Sherry, Vaccarino, Buckenham, & Herz, 1989;Volman, Grubb, & Schuett, 1997) and rodents (Jacobs, 1992;Jacobs & Spencer, 1994), foraging-related rate of movement in lacertid lizards (Day, Crews, & Wilczynski, 1999), home-range size in voles (Gaulin, 1992;Jacobs, Gaulin, Sherry, & Hoffman, 1990 Sherry, Jacobs, & Gaulin, 1992), and breeding-habitat complexity in petrels (Abbott, Walsh, Storey, Stenhause, & Harley, 1999) are all associated with enlarged Hp size, presumably due to the demands of spatial memory. In addition, seasonal variation in food-storing demands is associated with seasonal changes in Hp volume (Smulders, Sasson, & DeVoogd, 1995) in black-capped chickadees and rodents (Jacobs, 1996). Males have a larger Hp than females in a vole species in which males have larger home ranges but not in vole species that do not have sex differences in home range (Gaulin, 1992). These results provide evidence that environmental or experiential seasonal changes can alter Hp volume and that natural and sexual selection on a variety of spatial-related skills has produced a larger Hp in some species or sexes than in others.Although correlations of Hp volume with ecological demands for spatial ability are numerous, the specific mechanisms that contribute to such adult variation in the volume of the Hp are not well understood. We do know that species-specific reactions to spatial experience...

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Section: Cowbird Population Differencescontrasting

confidence: 91%

“…ISO = isolated females; CF = captive females; WCF = wild-caught females; CM = captive males; WCM = wild-caught males. f Measurements approximated from single study presented in Figure 2 (Sherry et al, 1993).…”

Section: Resultsmentioning

confidence: 99%

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Day

Guerra²,

Schlinger³

et al. 2008

Behavioral Neuroscience

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“…Female brown-headed cowbirds have a larger hippocampus than males, unlike related species that are not brood parasites [9,10]. Here, we show that this difference in brain morphology is associated with superior spatial memory in females as predicted from behavioural sex differences observed in the wild [6,8].…”

Section: Discussionmentioning

confidence: 58%

“…Female cowbirds, which spend their mornings in their egg-laying range either alone or followed by males, parasitize nests before sunrise when it is still dark and must, therefore, have an accurate memory of the locations of potential host nests [6,8]. Female brown-headed cowbirds have a larger hippocampus than males, whereas no sex difference exists in related species that are not brood parasites [9][10][11]. This difference in the hippocampus size between males and females may be present only in the breeding season [11].…”

Section: Introductionmentioning

confidence: 99%

Female cowbirds have more accurate spatial memory than males

Guigueno

Snow

MacDougall‐Shackleton

et al. 2014

Biol. Lett.

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Brown-headed cowbirds (Molothrus ater) are obligate brood parasites. Only females search for host nests and they find host nests one or more days before placing eggs in them. Past work has shown that females have a larger hippocampus than males, but sex differences in spatial cognition have not been extensively investigated. We tested cowbirds for sex and seasonal differences in spatial memory on a foraging task with an ecologically relevant retention interval. Birds were trained to find one rewarded location among 25 after 24 h. Females made significantly fewer errors than males and took more direct paths to the rewarded location than males. Females and males showed similar search times, indicating there was no sex difference in motivation. This sex difference in spatial cognition is the reverse of that observed in some polygynous mammals and is consistent with the hypothesis that spatial cognition is adaptively specialized in this brood-parasitic species.

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“…In birds and mammals, this function is mainly mediated by the hippocampus (30). A direct correlation has been found between hippocampal size and spatial ability both for orientation during migration and for retrieving scattered stored food (14,31). Furthermore, for some food-storing bird species, seasonal changes in hippocampal volume are accompanied by seasonal increases in neurogenesis, another form of hippocampal plasticity (32).…”

Section: Role Of the Hippocampus As A Dynamic Brain Structure That Admentioning

confidence: 99%

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

Magariños

McEwen

Saboureau

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

124

102

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The hippocampal formation is a highly plastic brain structure that undergoes structural remodeling in response to internal and external challenges such as metabolic imbalance and repeated stress. We investigated whether the extreme alterations in metabolic status that occur during the course of hibernation in European hamsters cause structural changes in the dendritic arborizations of the CA3 pyramidal neurons and their main excitatory afferents, the mossy fiber terminals (MFT), that originate in the dentate gyrus. We report that apical, but not basal, dendritic trees of Golgiimpregnated CA3 principal neurons are significantly shorter, less branched, and less spiny in hypothermic hamsters compared with active animals. After the induction of arousal from torpor, within 2 h, the apical dendritic lengths, branching patterns, and spine density estimations returned to levels found in active, euthermic hamsters. The ultrastructure of MFT in hibernating hamsters showed a significant reduction in synaptic vesicle density and in the percentage of MFT area covered by spine profiles. Awakened hamsters showed restoration of MFT morphology to that seen in active animals. MFT of torpid animals also showed a significant increase in the percentage area of mitochondrial profiles that remained higher 3 h after induced arousal from hibernation compared with euthermic controls. Thus, the torpid/awakening cycle of the hibernating European hamster causes a rapid and reversible morphological reorganization of intrahippocampal subregions involved in information processing. The reported reductions in morphological connectivity between the dentate gyrus and the CA3 subregions could underlie the cessation of exploratory activity and spatial navigation skills during hibernation.CA3 region ͉ hippocampus ͉ mossy fibers ͉ spines ͉ Golgi impregnation H ibernation is a highly regulated physiological response to adverse environmental conditions characterized by hypothermia and drastic reductions of metabolic rate (1). Hibernating species can adapt to anticipated scarcity in food supply and decreases in ambient temperature by storing food and increasing food intake for several weeks before winter starts (2). Once the animals enter into hibernation, they develop an energy conserving behavior and undergo deep bouts of hypothermia (or torpor) alternated with short euthermic intervals termed periodic arousals (3). By using fat stores as their primary source of energy and reducing carbohydrate metabolism, hibernating mammals sustain vital functions during prolonged periods without feeding and support periodic rewarming during interbout arousals (4).The physiological mechanisms triggering hibernation are very complex and far from being well known. Its seasonal occurrence is primarily regulated by the annual photoperiodic variations, and the neuroendocrine and neural mechanisms involved have been partly identified (5-8). The hippocampus, a target brain region for stressful challenges and adrenal steroids (9), has been postulated as a key structure in th...

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Females have a larger hippocampus than males in the brood-parasitic brown-headed cowbird.

Cited by 180 publications

References 32 publications

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Female cowbirds have more accurate spatial memory than males

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

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