Elephants Have Relatively the Largest Cerebellum Size of Mammals

Abstract

The current study used MR imaging to determine the volume of the cerebellum and its component parts in the brain of three adult male African elephants (Loxodonta africana) and compared this with published data from Asian elephants and other mammalian species including odontocete cetaceans, primates, chiropterans, insectivores, carnivores, and artiodactyls. The cerebellum of the adult elephant has a volume of $925 mL (average of both African and Asian species). Allometric analysis indicates that the elephant has the largest relative cerebellum size of all mammals studied to date. In addition, both odontocete cetaceans and microchiropterans appear to have large relative cerebellar sizes. The vermal and hemispheric components of the African elephant cerebellum are both large relative to other mammals of similar brain size, however, for odontocete cetaceans the vermal component is small and the hemispheric component is large. These volumetric observations are related to life-histories and anatomies of the species investigated. The current study provides context for one aspect of the elephant brain in the broader picture of mammalian brain evolution. Anat Rec, 295:661-672, 2012. V C 2012 Wiley Periodicals, Inc.

The Brain of the Horse: Weight and Cephalization Quotients

“…The cerebellum is the second largest component, and the CQ of 0.841 is in the range given for insectivores, Megachiropterans, and primates [Maseko et al, 2012], but it is well below those for cetaceans and both African and Asian elephants. The absolute weight (and the relative percentage values) of the brain divisions that we report for the horse are different from what has been reported for the zebra E. burchelli [Reep et al, 2007].…”

“…We also calculated the individual EQ of each adult horse, using their specific brain and body weights. To calculate the CQ, we applied the formula CQ = Cb vol / (0.145M b 0.978 ), proposed by Maseko et al [2012], in which Cb vol is the volume of the cerebellum (Cb vol × 1.04 = Cb mass × 0.96 [Weaver, 2005]) and M b is the brain mass (=brain weight). Since the weight of each brain component was determined on fixed specimens, we applied the conversion formula to obtain the weight of fresh tissue (see above).…”

Architectural Organization of the African Elephant Diencephalon and Brainstem

“…Prior to sectioning, all three brains underwent MR imaging ( fig. 1 ) to reveal the general anatomy of the diencephalon and brainstem of the elephant [full MRI protocol previously described in Manger et al, 2010Manger et al, , 2012Maseko et al, 2011Maseko et al, , 2012. As all three specimens showed a similar anatomy (i.e.…”

“…The inferior olivary complex is closely associated with the cerebellum and appears to play a crucial role in both motor learning and motor timing of non-rhythmic movements in the awake animal [De Zeeuw et al, 1998]. This increase in size of the inferior olivary complex appears to be linked to the increased size of the elephant cerebellum [Maseko et al, 2012] and the increased complexity of the cerebellar cortex [Maseko et al, 2013].…”

The Evolutions of Large Brain Size in Mammals: The ‘Over-700-Gram Club Quartet'

“…Recent studies are beginning to demonstrate that the elephant brain, in overall appearance is, unsurprisingly, a typical, but large, mammalian brain; however, it does possess specializations associated with the auditory and vocalization systems [Cozzi et al, 2001;Maseko et al, 2013b], with the portion of the motor system related to the timing of movements [Maseko et al, 2012[Maseko et al, , 2013a, the presence of von Economo neurons [Hakeem et al, 2009], and a very large, both in relative and absolute terms, cerebellum [Maseko et al, 2012[Maseko et al, , 2013a. In addition, it is evident that the morphological complexity of some of the pyramidal neurons in the frontal cortex rivals those seen in human frontal cortex .…”