Magnetic resonance images of the brain of a dwarf sperm whale (Kogia simus)

Abstract

Cetacean (dolphin, whale and porpoise) brains are among the least studied mammalian brains because of the difficulty of collecting and histologically preparing such relatively rare and large specimens. Among cetaceans, there exist relatively few studies of the brain of the dwarf sperm whale (Kogia simus). Magnetic resonance imaging (MRI) offers a means of observing the internal structure of the brain when traditional histological procedures are not practical. Therefore, MRI has become a critical tool in the study of the brain of cetaceans and other large species. This paper represents the first MRI-based anatomically labelled three-dimensional description of the dwarf sperm whale brain. Coronal plane sections of the brain of a sub-adult dwarf sperm whale were originally acquired and used to produce virtual digital scans in the other two orthogonal spatial planes. A sequential set of images in all three planes has been anatomically labelled and displays the proportions and positions of major neuroanatomical features.

Fig. 1

(a–j) Posterior-to-anterior sequence of originally acquired 2.0-mm-thick coronal magnetic resonance brain sections at 10-mm intervals, a labelled schematic illustration of each section, computer-generated images showing the level at which the section was taken in three orthogonal planes and a computer-generated three-dimensional reconstruction of the whole brain showing the brain digitally ‘cut’ at the level of the section.

Fig. 2

(a–j) Ventral-to-dorsal sequence of reconstructed ‘virtual’ 0.52-mm-thick horizontal sections at 5.2-mm intervals, a labelled schematic illustration of each section, computer-generated images showing the level at which the section was taken in three orthogonal planes and a computer-generated three-dimensional reconstruction of the whole brain showing the brain digitally ‘cut’ at the level of the section.

Fig. 3

(a–j) Midline-to-lateral sequence of reconstructed virtual 0.52-mm-thick sagittal sections through the left hemisphere at 5.2-mm intervals, a labelled schematic illustration of each section, computer-generated images showing the level at which the section was taken in three orthogonal planes and a computer-generated three-dimensional reconstruction of the whole brain showing the brain digitally ‘cut’ at the level of the section.