The corpus callosum enables integration and coordination of cognitive processing between the cerebral hemispheres. In the aging human brain, these functions are affected by progressive axon and myelin deteriorations, reflected as atrophy of the midsagittal corpus callosum in old age. In non-human primates, these degenerative processes are less pronounced as previous morphometric studies on capuchin monkey, rhesus monkeys, and chimpanzees do not find old-age callosal atrophy. In the present study, we extend these previous findings by studying callosal development of the olive baboon (Papio anubis) across the lifespan and compare it to chimpanzee and human data. For this purpose, total relative (to forebrain volume) midsagittal area, subsectional area, and regional thickness of the corpus callosum were assessed in 91 male and female baboons using non-invasive MRI-based morphometry. The studied age range was 2.5–26.6 years and lifespan trajectories were fitted using general additive modelling. Relative area of the total and anterior corpus callosum showed a positive linear trajectory. That is, both measures increased slowly but continuously from childhood into old age, and no decline was observed in old age. Thus, comparable with all other non-human primates studied to-date, baboons do not show callosal atrophy in old age. This observation lends supports to the notion that atrophy of the corpus callosum is a unique characteristic of human brain aging.

胼胝体能够整合和协调大脑半球之间的认知处理。在衰老的人脑中，这些功能受到进行性轴突和髓鞘退化的影响，表现为老年胼胝体中矢状体萎缩。在非人类灵长类动物中，这些退化过程不太明显，因为之前对卷尾猴、恒河猴和黑猩猩的形态测量研究没有发现老年胼胝体萎缩。在本研究中，我们通过研究橄榄狒狒的胼胝体发育来扩展这些先前的发现（Papio anubis) 整个生命周期，并将其与黑猩猩和人类数据进行比较。为此，使用基于 MRI 的无创形态测量法评估了 91 只雄性和雌性狒狒的总相对（相对于前脑体积）中矢状面积、亚截面面积和胼胝体区域厚度。研究的年龄范围为 2.5-26.6 岁，寿命轨迹使用通用加法建模拟合。总胼胝体和前胼胝体的相对面积呈正线性轨迹。也就是说，这两个指标从童年到老年都缓慢但持续地增加，并且在老年时没有观察到下降。因此，与迄今为止研究的所有其他非人类灵长类动物相比，狒狒在老年时不会表现出胼胝体萎缩。