Cetacean (dolphin, whale, and porpoise) brains are among the least studied mammalian brains because of the formidability of collecting and histologically preparing such relatively rare and large specimens. Magnetic resonance imaging offers a means of observing the internal structure of the brain when traditional histological procedures are not practical. Furthermore, internal structures can be analyzed in their precise anatomic positions, which is difficult to accomplish after the spatial distortions often accompanying histological processing. In this study, images of the brain of an adult bottlenose dolphin, Tursiops truncatus, were scanned in the coronal plane at 148 antero-posterior levels. From these scans a computer-generated three-dimensional model was constructed using the programs VoxelView and VoxelMath (Vital Images, Inc.). This model, wherein details of internal and external morphology are represented in three-dimensional space, was then resectioned in orthogonal planes to produce corresponding series of virtual sections in the horizontal and sagittal planes. Sections in all three planes display the sizes and positions of major neuroanatomical features such as the arrangement of cortical lobes and subcortical structures such as the inferior and superior colliculi, and demonstrate the utility of MRI for neuroanatomical investigations of dolphin brains. Anat Rec 264: [397][398][399][400][401][402][403][404][405][406][407][408][409][410][411][412][413][414] 2001.

Magnetic resonance imaging offers a means of observing the internal structure of the brain where traditional procedures of embedding, sectioning, staining, mounting, and microscopic examination of thousands of sections are not practical. Furthermore, internal structures can be analyzed in their precise quantitative spatial interrelationships, which is difficult to accomplish after the spatial distortions often accompanying histological processing. For these reasons, magnetic resonance imaging makes specimens that were traditionally difficult to analyze, more accessible. In the present study, images of the brain of a white whale (Beluga) Delphinapterus leucas were scanned in the coronal plane at 119 antero-posterior levels. From these scans, a computer-generated three-dimensional model was constructed using the programs VoxelView and VoxelMath (Vital Images, Inc.). This model, wherein details of internal and external morphology are represented in three-dimensional space, was then resectioned in orthogonal planes to produce corresponding series of "virtual" sections in the horizontal and sagittal planes. Sections in all three planes display the sizes and positions of such structures as the corpus callosum, internal capsule, cerebral peduncles, cerebral ventricles, certain thalamic nuclear groups, caudate nucleus, ventral striatum, pontine nuclei, cerebellar cortex and white matter, and all cerebral cortical sulci and gyri. Anat Key words: brain; neuroanatomy; cetacean; odontocete; white whale; Beluga; MRI Odontocetes (toothed whales, dolphins, and porpoises) have undergone a number of evolutionary modifications from their terrestrial ancestral state. Among these changes was a major increase in relative brain size. Several modern odontocete species possess encephalization levels second only to modern humans when brain-body allometry is taken into account (Ridgway and Brownson, 1984;Marino, 1998). An arguably equally dramatic transformation of odontocetes occurred in the anatomical structure and organization of their brains. Compared with many other mammalian brains, odontocete brain morphology is unusual in many respects. Researchers have stated that "…the lobular formations in the dolphin brain

To demonstrate the kinds of data that can be obtained non-destructively and non-invasively from preserved museum specimens using modern imaging technology the head region of a whole body fetal specimen of the common dolphin, Delphinus delphis, aged 8-9 months post-conception, was scanned using Magnetic Resonance Imaging (MRI). Series of scans were obtained in coronal, sagittal and horizontal planes. A digital three-dimensional reconstruction of the whole brain was prepared from the coronal series of scans. Sectional areas and three-dimensional volumes were obtained of the cerebral hemispheres and of the brainstem-plus-cerebellum. Neuroanatomical features identified in the scans include the major sulci of the cerebral hemispheres, well-differentiated regions of gray and white matter, the mesencephalic, pontine, and cervical flexures, the "foreshortened" appearance of the forebrain, and the large auditory inferior colliculi. These findings show that numerous features of the fetal common dolphin brain can be visualized and analyzed from MRI scans.

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The paradigms of the latter two configurations are believed to be unique. All modulation methods are based on the premise that the wall cannot be breached in any way and can therefore be viably implemented with power delivered wirelessly through the acoustic channel using ultrasound. Methods, results, and considerations for future research are discussed herein.