Montie Eric W, Schneider Gerald, Ketten Darlene R, Marino Lori, Touhey Katie E, Hahn Mark E
Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Anat Rec (Hoboken). 2008 Mar;291(3):263-82. doi: 10.1002/ar.20654.
The structure and development of the brain are extremely difficult to study in free-ranging marine mammals. Here, we report measurements of total white matter (WM), total gray matter (GM), cerebellum (WM and GM), hippocampus, and corpus callosum made from magnetic resonance (MR) images of fresh, postmortem brains of the Atlantic white-sided dolphin (Lagenorhynchus acutus) imaged in situ (i.e., the brain intact within the skull, with the head still attached to the body). WM:GM volume ratios of the entire brain increased from fetus to adult, illustrating the increase in myelination during ontogeny. The cerebellum (WM and GM combined) of subadult and adult dolphins ranged from 13.8 to 15.0% of total brain size, much larger than that of primates. The corpus callosum mid-sagittal area to brain mass ratios (CCA/BM) ranged from 0.088 to 0.137, smaller than in most mammals. Dolphin hippocampal volumes were smaller than those of carnivores, ungulates, and humans, consistent with previous qualitative results assessed from histological studies of the bottlenose dolphin brain. These quantitative measurements of white matter, gray matter, corpus callosum, and hippocampus are the first to be determined from MR images for any cetacean species. We establish here an approach for accurately determining the size of brain structures from in situ MR images of stranded, dead dolphins. This approach can be used not only for comparative and developmental studies of marine mammal brains but also for investigation of the potential impacts of natural and anthropogenic chemicals on neurodevelopment and neuroanatomy in exposed marine mammal populations.
在自由放养的海洋哺乳动物中，大脑的结构和发育极难研究。在此，我们报告了对大西洋白边海豚（Lagenorhynchus acutus）新鲜、死后大脑的磁共振（MR）图像进行测量得到的全脑白质（WM）、全脑灰质（GM）、小脑（WM和GM）、海马体和胼胝体的数据，这些大脑是在原位成像的（即大脑完整地位于头骨内，头部仍与身体相连）。全脑的WM:GM体积比从胎儿期到成年期增加，表明个体发育过程中髓鞘形成增加。亚成年和成年海豚的小脑（WM和GM总和）占全脑大小的13.8%至15.0%，远大于灵长类动物。胼胝体矢状中面面积与脑质量比（CCA/BM）在0.088至0.137之间，比大多数哺乳动物小。海豚海马体的体积小于食肉动物、有蹄类动物和人类，这与之前对宽吻海豚大脑组织学研究得出的定性结果一致。这些对白质、灰质、胼胝体和海马体的定量测量是首次从任何鲸类物种的MR图像中确定的。我们在此建立了一种从搁浅死亡海豚的原位MR图像准确确定脑结构大小的方法。这种方法不仅可用于海洋哺乳动物大脑的比较和发育研究，还可用于调查天然和人为化学物质对受暴露海洋哺乳动物种群神经发育和神经解剖学的潜在影响。
