爱思唯尔期刊《学习与记忆神经生物学》(Neurobiology of Learning and Memory)在线发表了美国芝加哥大学的一项最新研究，研究发现体内皮质醇含量适中的松鼠在学习和适应环境等方面都比含皮质醇偏高或是偏低的松鼠强。
皮质醇是肾上腺在应激反应里产生的一种类激素，压力状态下身体需要皮质醇来维持正常生理机能。研究中研究人员模拟出一个与松鼠窝相连的自然迷宫以探测其辨别能力，同时研究人员人为地改变了一些松鼠的体内皮质醇含量。结果发现，体内皮质醇含量适中的松鼠用9次会找到它们的“家”，而对于那些皮质醇含量偏高或偏低的松鼠则平均都需要13至14次的尝试才能做到。同时，研究人员还对体内皮质醇含量的不同的松鼠对应险情能力方面做了测试，研究发现同样皮质醇含量适中的松鼠能力要强。
目前，对于人体内皮质醇偏低会如何影响其学习方面还尚不清楚。科学家希望动物体内皮质醇含量对其学习方面的影响，能够对研究人体皮质醇水平对人学习能力的影响有所启发。（科学网 于乃森/编译）
生物谷推荐原始出处：
(Neurobiology of Learning and Memory)，doi:10.1016/j.nlm.2007.11.002，Jill M. Mateo
Inverted-U shape relationship between cortisol and learning in ground squirrels
Jill M. Mateo, a,
aDepartment of Comparative Human Development & The Institute for Mind and Biology, 5730 South Woodlawn Avenue, The University of Chicago, Chicago, IL 60637, USA
Received 16 October 2007; revised 18 November 2007; accepted 19 November 2007. Available online 4 March 2008.
Abstract
Adrenal hormones regulate glucose levels, responses to unpredictable stressors and modulate cognition. Glucocorticoids can have an inverted-U shape relationship with cognition, as very low or high levels impair, whereas moderate elevations facilitate, acquisition and retention of memories. To date these relationships have been tested with humans and rodents in laboratory settings rather than with wild animals in biologically relevant contexts. This study examined whether the elevated cortisol observed in juvenile Belding’s ground squirrels (Spermophilus beldingi) at natal emergence might promote both acquisition of adaptive responses to this species’ two alarm calls warning of predators and memory of the spatial configuration of mothers’ territories. Both experimentally increased and decreased basal cortisol levels interfere with acquisition and retention of an association between a warning call and the appropriate response compared with naturally occurring moderately elevated cortisol. Further, decreased cortisol impairs learning of a novel, complex spatial maze. Thus in the field the brief elevation of cortisol at emergence might facilitate acquisition of spatial memory of a three-dimensional environment and responses to alarm calls during a sensitive period of learning. This novel demonstration of the inverted-U shape function in a wild animal suggests that natural selection has favored a hormonal profile facilitating rapid acquisition of important survival behaviors.
