Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California-San Diego, La Jolla, CA, 92093, USA.
Department of Radiology, University of California-San Diego, La Jolla, CA, 92093, USA.
Brain Struct Funct. 2018 May;223(4):1697-1711. doi: 10.1007/s00429-017-1525-9. Epub 2017 Nov 30.
Brain enlargement is associated with concomitant growth of interneuronal distance, increased conduction time, and reduced neuronal interconnectivity. Recognition of these functional constraints led to the hypothesis that large-brained mammals should exhibit greater structural and functional brain lateralization. As a taxon with the largest brains in the animal kingdom, Cetacea provides a unique opportunity to examine asymmetries of brain structure and function. In the present study, diffusion tensor imaging and tractography were used to investigate cerebral white matter asymmetry in the bottlenose dolphin (Tursiops truncatus). Widespread white matter asymmetries were observed with the preponderance of tracts exhibiting leftward structural asymmetries. Leftward lateralization may reflect differential processing and execution of behaviorally variant sensory and motor functions by the cerebral hemispheres. The arcuate fasciculus, an association tract linked to human language evolution, was isolated and exhibited rightward asymmetry suggesting a right hemisphere bias for conspecific communication unlike that of most mammals. This study represents the first examination of cetacean white matter asymmetry and constitutes an important step toward understanding potential drivers of structural asymmetry and its role in underpinning functional and behavioral lateralization in cetaceans.
脑增大与神经元距离的同时生长、传导时间的增加和神经元间连接性的降低有关。对这些功能限制的认识导致了一个假设，即大脑较大的哺乳动物应该表现出更大的结构和功能大脑偏侧化。作为动物王国中大脑最大的分类群，鲸目动物为研究大脑结构和功能的不对称性提供了一个独特的机会。在本研究中，使用弥散张量成像和束流追踪技术研究了宽吻海豚（Tursiops truncatus）的大脑白质不对称性。观察到广泛的白质不对称性，大多数束流表现出左向结构不对称性。左侧偏侧化可能反映了大脑半球对行为变异的感觉和运动功能的不同处理和执行。弓状束是与人类语言进化相关的联合束，它被分离出来并表现出右侧不对称性，这表明与大多数哺乳动物不同，右侧半球偏向于同种间交流。本研究代表了对鲸目动物白质不对称性的首次检查，是朝着理解结构不对称性的潜在驱动因素及其在鲸目动物功能和行为偏侧化中的作用迈出的重要一步。
