Huchzermeyer Christine, Husemann Pamela, Lieshoff Carsten, Bischof Hans-Joachim
Lehrstuhl für Verhaltensforschung, Universität Bielefeld, Germany.
Behav Brain Res. 2006 Jul 15;171(1):154-61. doi: 10.1016/j.bbr.2006.03.034. Epub 2006 May 4.
Sexual imprinting is an early learning process by which young birds acquire the characteristics of a potential sexual partner. The physiological basis of this learning process is an irreversible reduction of dendritic spines in two forebrain areas, the LNM (lateral nido-mesopallium) and the MNM (medial nido-mesopallium). The aim of the present study was to investigate whether these two brain areas are activated if the imprinted stimulus is presented to the adult bird after the end of the sensitive period. One group of zebra finch males was reared by their own parents. These birds, as adults, showed an exclusive preference for their own species in choice tests between a zebra finch and a Bengalese finch female. If exposed as adults to a zebra finch female, LNM and MNM showed lower activation, as measured by ZENK expression, compared to males exposed to a Bengalese finch female. A second group was reared by Bengalese finches and was exposed at day 100 to a zebra finch female for 1 week. As shown earlier, this regime leads to mixed choices, the birds are courting Bengalese and zebra finch females with a fixed ratio (preference score). If these birds were exposed to a zebra finch female as adults, the ZENK expression within LNM was much higher compared to group 1, and it showed a strong tendency to correlate negatively with the preference score: Birds with higher zebra finch preference showed lower activation compared to those with a low zebra finch and a high Bengalese finch preference. We propose that higher ZENK activation in group 2 is due to the rearing by a foster species which may result in a more complex neuronal network. The negative relation between activation and preference score may be explained by special properties of the LNM and MNM networks.
性印记是一种早期学习过程，幼鸟通过这一过程习得潜在性伴侣的特征。这一学习过程的生理基础是前脑两个区域——外侧巢状中脑皮层（LNM）和内侧巢状中脑皮层（MNM）——树突棘的不可逆减少。本研究的目的是调查在敏感期结束后，若将印记刺激呈现给成年鸟类，这两个脑区是否会被激活。一组斑胸草雀雄性由其亲生父母抚养长大。成年后，在斑胸草雀和孟加拉雀雌性之间的选择测试中，这些鸟表现出对自身物种的排他性偏好。与接触孟加拉雀雌性的雄性相比，成年后接触斑胸草雀雌性的鸟，其LNM和MNM的激活程度（通过ZENK表达来衡量）较低。第二组由孟加拉雀抚养长大，并在第100天接触斑胸草雀雌性1周。如先前所示，这种饲养方式会导致混合选择，这些鸟会以固定比例（偏好分数）向孟加拉雀和斑胸草雀雌性求偶。如果这些鸟成年后接触斑胸草雀雌性，与第一组相比，LNM内的ZENK表达要高得多，并且显示出与偏好分数呈负相关的强烈趋势：与斑胸草雀偏好低而孟加拉雀偏好高的鸟相比，斑胸草雀偏好高的鸟激活程度较低。我们认为，第二组中较高的ZENK激活是由于由寄养物种抚养长大，这可能导致更复杂的神经网络。激活与偏好分数之间的负相关关系可能由LNM和MNM网络的特殊性质来解释。
