Lee Minwoo, Gonzalez Amber, Rilling James K
Department of Psychology, College of Human Ecology, Cornell University, Ithaca, NY 14853, United States.
Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, United States.
Soc Cogn Affect Neurosci. 2025 May 14;20(1). doi: 10.1093/scan/nsaf034.
Grandmothers enhance grandchild survival and maternal health through caregiving. Comparative evidence suggests that human grandmotherhood reflects a unique life history strategy promoting the inclusive fitness of post-reproductive females. Despite its evolutionary importance, the proximate neural mechanisms supporting grandmaternal caregiving remain unclear. This study uses functional magnetic resonance imaging (fMRI) and multivariate approaches to investigate how grandmaternal brains encode information about grandchildren and translate it into caregiving. Forty-seven grandmothers (age = 59.1 ± 7 years) completed an fMRI task viewing photos of a grandchild, the grandchild's parent, unfamiliar individuals, and nonhuman objects. Multi-voxel activation patterns associated with these stimuli were analyzed using representational similarity analysis, focusing on the hypothalamic and mesolimbic regions critical for mammalian parenting. Results reveal that grandchildren had the most distinct multi-voxel pattern of activation within these regions, potentially reflecting the grandmothers' motivational readiness to engage in grandmaternal caregiving. Indeed, greater neural dissimilarity between the grandchild and other social categories correlated with higher self-reported affection and supportive behaviors towards grandchildren, particularly in paternal grandmothers. Our findings provide novel insights into the mechanisms of grandmaternal caregiving that enhances inclusive fitness.
祖母通过照料孙辈来提高孙辈的存活率和产妇的健康水平。比较证据表明，人类祖母身份反映了一种独特的生活史策略，可促进绝经后女性的广义适合度。尽管其在进化上具有重要意义，但支持祖母照料行为的近因神经机制仍不清楚。本研究使用功能磁共振成像（fMRI）和多变量方法来探究祖母的大脑如何编码有关孙辈的信息并将其转化为照料行为。47名祖母（年龄 = 59.1 ± 7岁）完成了一项fMRI任务，观看孙辈、孙辈父母、陌生人和非人类物体的照片。使用表征相似性分析来分析与这些刺激相关的多体素激活模式，重点关注对哺乳动物养育至关重要的下丘脑和中脑边缘区域。结果显示，在这些区域内，孙辈具有最独特的多体素激活模式，这可能反映了祖母参与祖母照料行为的动机准备。事实上，孙辈与其他社会类别之间更大的神经差异与更高的自我报告的对孙辈的喜爱和支持行为相关，尤其是在祖母方面。我们的研究结果为祖母照料行为增强广义适合度的机制提供了新的见解。
