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An overview of the central nervous system of the elephant through a critical appraisal of the literature published in the XIX and XX centuries
Abstract
The two species of elephants (Indian: Elephas maximus and African: Loxodonta africana) possess the largest brain among land mammals. Due to its size, the elephant brain is discussed in virtually every paper dealing with the evolution of the central nervous system of mammals and comparative brain size. Studies on the social habits of elephants also deal with the skills and the "intelligence" and brain size of these species. Yet most of the descriptions and conclusions reported in comparative studies rely on second-hand data derived from investigations performed several decades before, often dating as far back as the XIX century. Furthermore, many of the original papers actually describing gross and detailed features of the brain of elephants are either no longer available, are written in languages other than English, or are difficult to trace. The present study gives a short description of the anatomy of the central nervous system of elephants, with special attention to its distinctive features, reports all available literature on the subject, and briefly discusses its origins and rationale.
... The brains of extinct Proboscideans, including mammoths, have not been the object of frequent study (Jerison, 1973;Cozzi et al., 2001). Even though several well-preserved frozen mummies of the large mammals, including woolly mammoths, have been found in the Siberian permafrost (Zalenskii, 1903;Zimmerman and Tedford, 1976;Vereschagin and Michelson, 1981), our current knowledge of the structure of the woolly mammoth brain is based solely on endocranial casts, and even these data are not extensively covered in the literature (Benoit et al., 2013;Manger et al., 2013). ...
... The brains of extant elephants evince a generally Eutherian mammal structure, but there are several specific features found only in this group (Cozzi et al., 2001;Shoshani et al., 2006). The extant elephants have the largest terrestrial brains (Cozzi et al., 2001;Shoshani et al., 2006;Manger et al., 2009), and the cerebral cortex appears to have extensive parietal and temporal lobes (Cozzi et al., 2001;Shoshani et al., 2006). ...
... The brains of extant elephants evince a generally Eutherian mammal structure, but there are several specific features found only in this group (Cozzi et al., 2001;Shoshani et al., 2006). The extant elephants have the largest terrestrial brains (Cozzi et al., 2001;Shoshani et al., 2006;Manger et al., 2009), and the cerebral cortex appears to have extensive parietal and temporal lobes (Cozzi et al., 2001;Shoshani et al., 2006). Although the cerebral cortex is extensively gyrencephalic, it is no more gyrencephalic than would be expected for its brain mass . ...
This study presents the results of an examination of the mummified brain of a pleistocene Woolly mammoth (Mammuthus primigenius) recovered from the Yakutian permafrost in Siberia, Russia. This unique specimen (39 440 - 38 850 years BP) provides the rare opportunity to compare the brain morphology of this extinct species with a related extant species, the African elephant (Loxodonta africana). An anatomical description of the preserved brain of the Woolly mammoth is provided, along with a series of quantitative analyses of various brain structures. These descriptions are based on visual inspection of the actual specimen as well as the qualitative and quantitative comparison of CT imaging data obtained for the Woolly mammoth in comparison to MR imaging data from three African elephant brains. In general, the brain of the Woolly mammoth specimen examined, estimated to weigh between 4230 - 4340 g, showed the typical shape, size and gross structures observed in extant elephants. The quantitative comparative analyses of various features of the brain, such as the amygdala, corpus callosum, cerebellum and gyrnecephalic index, all indicate that the brain of the Woolly mammoth specimen examined has many similarities with that of modern African elephants. The analysis provided herein indicates that a specific brain type representative of the Elephantidae is likely to be a feature of this mammalian family. In addition, the extensive similarities between the Woolly mammoth brain with the African elephant brain indicates that the specializations observed in the extant elephant brain are likely to have been present in the Woolly mammoth. This article is protected by copyright. All rights reserved.
© 2015 Wiley Periodicals, Inc.
... It has been consistently noted, in both a qualitative and quantitative sense, that elephants have large cerebellums, larger than in both humans and cetaceans (Beddard, 1893;Precechtel, 1925;Haug, 1970;Lange, 1971;Cozzi et al., 2001), (Fig. 1). Shoshani et al. (2006) described the gross anatomical appearance of the elephant cerebellum in great detail, and while there are some specific characteristics, such as complex foliation and an enlarged lateral recess of the fourth ventricle, the general appearance is not unusual apart from some asymmetries in fissure patterns between the two cerebellar hemispheres (Beddard, 1893). ...
... All three groups have unusual systems of vocalization (infrasound in elephants, Garstang, 2004;echolocation in cetaceans and microchiropterans, Rendell et al., 1999;Speakman, 2001). In both the elephants and odontocete cetaceans, this specialized vocalization appears to be associated with an expansion of the periaqueductal grey matter into a specific nucleus ellipticus (Cozzi et al., 2001;Manger, 2006;Shoshani et al., 2006). Associated with the production of these vocalizations is a complex air sac anatomy within the blowhole of odontocete cetaceans (Reidenberg and Laitman, 2008), an association between flapping flight and laryngeal vocalization in microchiropterans (Speakman, 2001), and an unusual unpaired appendage, the trunk, in elephants (Endo et al., 2001) although the mechanism for the production of infrasound in elephants is currently unknown. ...
... The hemispheric portion of the cerebellum has a strong association with the dorsal thalamus and cerebral cortex and is involved in complex goal-directed limb movements, where it regulates movements requiring the integration of motor behaviors with cortical functions requiring learning and also with the control of eye movements (Stein and Glickstein, 1992). The large size of the cerebellar hemispheres appears to be coordinated with an increase in size of the inferior olivary complex of elephants (Cozzi et al., 2001;Shoshani et al., 2006). The complexity of the trunk musculature (Endo et al., 2001), the learning of the use of the trunk in the infant elephant (Lee and Moss, 1999), the complex use of the trunk for environmental manipulation in the adult elephant, the observation that the organization of the elephant retina reflects that they use trunk-eye coordination extensively (Pettigrew et al., 2010), and that the majority of the representation of the body surface in the hemispheric cerebellar cortex is that of the face in other mammals (e.g., Welker et al, 1988;Bower, 2011), all speak towards the control of the trunk, especially in cortically controlled learning of complex movements, as the main driving factor behind hemispheric enlargement in the elephant cerebellum. ...
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
... Despite this large brain mass, very little is actually known about the structure, and thus, functional capacities, of the proboscidean brain. A recent review of the neuroanatomical data available for proboscidean brains (Cozzi et al., 2001) reported that only 52 scientific papers have been published that are specifically dedicated to structural aspects of the brain, and that 20 of these were written in the 19th century. Moreover, 46% of these 52 articles were written in French, German, or Italian. ...
... Comparatively, there is a wealth of information on the large brains of primates and cetaceans. It was concluded by Cozzi et al. (2001) that the lack of interest in the proboscidean brain is: ". . .probably due to the feeling that no 'front line' discovery can be derived from these studies. . ...
... funding agencies. Cozzi et al. (2001) further reason that the wide gap in the amount of knowledge derived for the cetacean and proboscidean brain results from the military interest in the behaviour and physiology of the dolphins and whales, and the need for knowledge of the cetacean brain from countries that previously were whaling countries with a specific need for commercial exploitation. ...
The current correspondence describes the in situ perfusion-fixation of the brain of the African elephant. Due to both the large size of proboscidean brains and the complex behaviour of these species, the acquisition of good quality material for comparative neuroanatomical analysis from these species is important. Three male African elephants (20-30 years) that were to be culled as part of a larger population management strategy were used. The animals were humanely euthanized and the head removed from the body. Large tubes were inserted into to the carotid arteries and the cranial vasculature flushed with a rapid (20 min) rinse of 100 l of cold saline (4 degrees C). Following the rinse the head was perfusion-fixed with a slower rinse (40 min) of 100 l of cold (4 degrees C) 4% paraformaldehyde in 0.1M phosphate buffer. This procedure resulted in well-fixed neural and other tissue. After perfusion the brains were removed from the skull with the aid of power tools, a procedure taking between 2 and 6h. The brains were immediately post-fixed in the same solution for 72 h at 4 degrees C. The brains were subsequently placed in a sucrose solution and finally an antifreeze solution and are stored in a -20 degrees C freezer. The acquisition of high quality neural material from African elephants that can be used for immunohistochemistry and electron microscopy is of importance in understanding the "hardware" underlying the behaviour of this species. This technique can be used on a variety of large mammals to obtain high quality material for comparative neuroanatomical studies.
... The African elephant, Loxodonta africana, is the largest living land mammal. It has a brain comparable in size and complexity to those of cetaceans and humans (Cozzi et al., 2001). This makes the elephant brain of interest both because it is an extreme data point in studies of brain structure sizes or connectivity, and because elephants, like primates, are long-lived species possessed of a complex social structure (Payne, 2003;Sukumar, 2003). ...
... Recently, four hierarchical tiers of social organization were demonstrated in the African el-ephant, the first such society revealed in a nonhuman animal (Wittemyer et al., 2005). However, in a review of the available literature on the elephant nervous system, Cozzi et al. (2001) found that elephant brain size and architecture information has mostly been taken from only a few original investigations, some dating from as far back as the 19th century. Much literature is characterized by general statements such as that the cerebral cortex was "highly convoluted" and the gray matter was "thick," although Haug (1970) made quantitative as well as qualitative measurements. ...
... Compared to a human or great ape brain, the elephant brain is expanded laterally, with very large, distinct temporal lobes. The telencephalon is similar in shape to those of the minke (Balaenoptera acutorostrata) (Igarashi and Kamiya, 1972) and humpback (Megaptera novaeangliae) (Cozzi et al., 2001) whales, but is less compressed in the rostrocaudal axis than in the Delphinidae (Igarashi and Kamiya, 1972;Marino et al., 2004). The large cerebellum is located posterior to and on a level with the rest of the brain, as in other quadrupeds (Igarashi and Kamiya, 1972). ...
We acquired magnetic resonance images of the brain of an adult African elephant, Loxodonta africana, in the axial and parasagittal planes and produced anatomically labeled images. We quantified the volume of the whole brain (3,886.7 cm3) and of the neocortical and cerebellar gray and white matter. The white matter-to-gray matter ratio in the elephant neocortex and cerebellum is in keeping with that expected for a brain of this size. The ratio of neocortical gray matter volume to corpus callosum cross-sectional area is similar in the elephant and human brains (108 and 93.7, respectively), emphasizing the difference between terrestrial mammals and cetaceans, which have a very small corpus callosum relative to the volume of neocortical gray matter (ratio of 181-287 in our sample). Finally, the elephant has an unusually large and convoluted hippocampus compared to primates and especially to cetaceans. This may be related to the extremely long social and chemical memory of elephants.
... Despite these large brains, until recently very little was known about the structure, and through inference, functional capacities of the elephant brain. A 2001 review of the neuroanatomical data available for the elephant brain (Cozzi et al. 2001) demonstrated that only 52 scientific papers had been published that were specifically dedicated to structural aspects of the elephant brain, and that 20 of these were written in the nineteenth century. It was concluded by Cozzi et al. (2001, p.255) that the lack of interest in the elephant brain is: "…probably due to the feeling that no 'front line' discovery can be derived from these studies…", and a lack of interest in support for such studies from funding agencies. ...
... One of the most striking features of the elephantine brain surface anatomy is the extent to which the cerebral cortex is fissured and folded, termed gyrencephaly (Cozzi et al. 2001;Shoshani et al. 2006). It has been shown that, broadly across mammalian species, the larger the brain (in absolute size), the more gyrencephalic the cerebral cortex (Manger et al. 2012). ...
The elephant brain is famous for its higher than average encephalization quotient, memory capacities, large cerebellum, large facial and trigeminal nerves, and the extensive repertoire of complex behaviors and social interactions it produces, the last of which being supported by infrasonic communication. The evolutionary history of Proboscidea is amongst the best-documented among mammals but knowledge of the group’s paleoneurological history remains comparatively fragmentary. Here, we summarize and build upon more than 150 years of research on the evolution of the proboscidean nervous system. We find that the morphology of the endocranial cast and bony labyrinth of the basal-most proboscideans is consistent with the generalized plesiomorphic conditions for placental mammals (e.g. linearly organized brain parts, low encephalization quotient, presence of a secondary common crus), whereas their conditions become essentially elephant-like in the Elephantimorpha around the Oligocene. This suggests that a higher encephalization quotient and adaptations to low-frequency hearing (e.g. loss of the secondary bony lamina) evolved in parallel with the formation and evolution of a trunk, adaptation to a drier environment, and a higher body mass. We hypothesize that these structures co-evolved as a response to the changing climate in the Oligocene.
... The neurons of this strikingly large structure are unique in shape and different from any other type of neuron in the central nervous system (Nieto and Nieto 1984). This structure includes an area generally occupied by the red nucleus in other mammals and may correspond to the nucleus medialis anterior (Cozzi et al. 2000). The functional significance of this structure is undetermined but may be related to controlling movements in the blowhole region, and/or oculomotor movements (Nieto and Nieto 1984), given that analogous structures in other mammals appear to control facial muscles (Cozzi et al. 2000). ...
... This structure includes an area generally occupied by the red nucleus in other mammals and may correspond to the nucleus medialis anterior (Cozzi et al. 2000). The functional significance of this structure is undetermined but may be related to controlling movements in the blowhole region, and/or oculomotor movements (Nieto and Nieto 1984), given that analogous structures in other mammals appear to control facial muscles (Cozzi et al. 2000). ...
The pantropical spotted dolphin (Stenella attenuata) is found worldwide,
primarily in tropical waters (Perrin et al. 1987, Perrin 2009) but has received the most
attention in the eastern tropical Pacific Ocean (ETP) where mortality due to the yellowfin
tuna purse-seine fishery between about 1960 and 1980 reduced one population to
depleted status (Smith 1983), leading to decades of research directed toward population
recovery. Subsequent to 1990, changes in fishery operations dramatically decreased
fishery-related mortality, but spotted dolphin abundance has not recovered as expected
(Wade et al. 2007). In an effort to determine whether factors related to form, function
and or pathology in spotted dolphins may be contributing to this apparent lack of
population recovery in the ETP, we reviewed spotted dolphin literature available through
2012. We relate the results of this literature review to potential interactions with the ETP
tuna purse-seine fishery. Although the majority of the data were collected from
specimens killed in tuna purse-seine nets in the ETP, we reviewed and include results of
studies without regard to geographic origin.
... The neurons of this strikingly large structure are unique in shape and different from any other type of neuron in the central nervous system (Nieto and Nieto 1984). This structure includes an area generally occupied by the red nucleus in other mammals and may correspond to the nucleus medialis anterior (Cozzi et al. 2000). The functional significance of this structure is undetermined but may be related to controlling movements in the blowhole region, and/or oculomotor movements (Nieto and Nieto 1984), given that analogous structures in other mammals appear to control facial muscles (Cozzi et al. 2000). ...
... This structure includes an area generally occupied by the red nucleus in other mammals and may correspond to the nucleus medialis anterior (Cozzi et al. 2000). The functional significance of this structure is undetermined but may be related to controlling movements in the blowhole region, and/or oculomotor movements (Nieto and Nieto 1984), given that analogous structures in other mammals appear to control facial muscles (Cozzi et al. 2000). ...
... Elephants have the largest absolute brain size of any land animal: 5.5 kg in Asian elephants and 6.5 kg in African savannah elephants (16)(17)(18). These values are Ϸ4 times the average brain mass of humans (9,19). ...
... Furthermore, several lines of indirect evidence suggest that the elephant neocortex is likely to require a great deal of energy on a neuron-specific basis. The elephant neocortex has a relatively low density of very largesized neurons (41,42) with extensive dendritic arborization (16), suggesting that each receives a relatively large number of synapses from interconnecting axons as compared with a large-brained primate (43). Accordingly, the interneuronal space in the elephant neocortex is occupied by a remarkably high density of glial cells (42). ...
... It does not, however, give the best indication of 'brain-power': as with any computational system, to assess power it is the actual number of processing units available for use that is important (Byrne, 1996). Elephants have the largest absolute brain size among land animals: up to 5.5 kg in Asian elephants and up to 6.5 kg in African savannah elephants (Cozzi, Spagnoli, & Bruno, 2001;Shoshani, Kupsky, & Marchant, 2006). Although neurons are less densely packed in elephant brains than in primates', elephant brains nevertheless contain as many cortical neurons as do human brains (Roth & Dicke, 2005). ...
... Although neurons are less densely packed in elephant brains than in primates', elephant brains nevertheless contain as many cortical neurons as do human brains (Roth & Dicke, 2005). Moreover, the pyramidal neurons are larger than in humans and most other species, with a large dendritic tree giving the potential for many more connections, and perhaps hinting at superior learning and memory skills (Cozzi, et al., 2001). Send There is a considerable body of theory and supportive data to suggest that living in an extensive social network often correlates with, and likely promotes, cognitive sophistication . ...
... Brain Size and Complexity Until recently, only scant information was available on the brains of elephants, with the majority of the literature based on only a few specimens (Cozzi, Spagnoli, and Bruno 2001). Recent work has added to our knowledge (Hakeem et al. 2005;Shoshani, Kupsky, and Marchant 2006). ...
... The brains of Asian and African elephants rank among the highest of all animals for absolute and relative mass and cortical expansion and complexity, features comparable only to those of some of the cetaceans, the great apes, and humans. Weighing 4.5-6.5 kilograms, the elephant's brain is the largest in absolute mass among land mammals (Cozzi et al. 2001), with the brain of E. maximus weighing up to 5.5 kilograms, and that of L. africana being slightly heavier and larger. The temporal lobes of the elephant's brain, which are thought to function in recognition, storage and retrieval of information related to sight, touch, smell, and hearing, are especially large and extremely complex (Shoshani 1998;Shoshani et al. 2006). ...
... It does not, however, give the best indication of 'brain-power': as with any computational system, to assess power it is the actual number of processing units available for use that is important (Byrne, 1996). Elephants have the largest absolute brain size among land animals: up to 5.5 kg in Asian elephants and up to 6.5 kg in African savannah elephants (Cozzi, Spagnoli, & Bruno, 2001;Shoshani, Kupsky, & Marchant, 2006). Although neurons are less densely packed in elephant brains than in primates', elephant brains nevertheless contain as many cortical neurons as do human brains (Roth & Dicke, 2005). ...
... Although neurons are less densely packed in elephant brains than in primates', elephant brains nevertheless contain as many cortical neurons as do human brains (Roth & Dicke, 2005). Moreover, the pyramidal neurons are larger than in humans and most other species, with a large dendritic tree giving the potential for many more connections, and perhaps hinting at superior learning and memory skills (Cozzi, et al., 2001). Send There is a considerable body of theory and supportive data to suggest that living in an extensive social network often correlates with, and likely promotes, cognitive sophistication . ...
On many of the staple measures of comparative psychology, elephants show no obvious differences from other mammals, such as primates: discrimination learning, memory, spontaneous tool use, etc. However, a range of more naturalistic mea- sures have recently suggested that elephant cognition may be rather different. Wild elephants sub-categorize humans into groups, independently making this classification on the basis of scent or colour. In number discrimination, elephants show no effects of absolute magnitude or relative size disparity in making number judgements. In the social realm, elephants show empathy into the problems faced by others, and give hints of special abilities in cooperation, vocal imitation and per- haps teaching. Field data suggest that the elephant's vaunted reputation for memory may have a factual basis, in two ways. Elephants' ability to remember large-scale space over long periods suggests good cognitive mapping skills. Elephants' skill in keeping track of the current locations of many family members implies that working memory may be unusually devel- oped, consistent with the laboratory finding that their quantity judgements do not show the usual magnitude ef fects.
... Nevertheless, despite elephants' status as the largest living terrestrial mammal, very little is known about the brain of this species. Prior to 2001, only a few original articles had specifically focused on the elephant central nervous system (Cozzi et al. 2001). Although the gross anatomy of the *5 kg adult elephant brain has been investigated in the last decade (Kupsky et al. 2001; Hakeem et al. 2005 Hakeem et al. , 2009 Shoshani et al. 2006; Manger et al. 2010), virtually nothing is known about the microstructural morphology of its neurons. ...
... Indeed, until recently, the only apparent insight into elephant cortical neuromorphology was a single camera lucida drawing from an Indian elephant (Elephas maximus; Barasa and Shochatovitz 1961 ). Reasons for this poverty of data are many (Cozzi et al. 2001), but include a propensity for neuroscientists to focus on the rodent and primate species commonly used in biomedical research (Manger et al. 2008), and a lack of well-preserved elephant brain tissue suitable for histological analysis. This latter issue was recently addressed by Manger et al. (2009), who were able to fix the brains of wild African elephants (Loxodonta africana) by postmortem, carotid cannulationperfusion . ...
... Qualitative impressions of the surface, and sections through the cerebral cortex, of elephant and cetacean brains indicate that the cerebral hemispheres of these species are highly gyrencephalic (see, e.g., Cozzi et al., 2001;Shoshani et al., 2006;Oelschl€ ager and Oelschl€ ager, 2009). The aim of the current study is to fill the gaps in our knowledge of the quantitative GI measurements for elephants and cetaceans and to identify how the relationship between GI and brain mass in cetaceans and elephants compares with that of species from other mammalian orders. ...
... Though more gyrencephalic than would be expected for a carnivore with a 5-kg brain, the elephant is as gyrencephalic as would be expected for a primate with a 5-kg brain. This result confirms previous qualitative observations that the cerebral cortex of the elephant is significantly gyrencephalic (Cozzi et al., 2001;Shoshani et al., 2006) but tempers this conclusion with the demonstration that it is not more gyrencephalic than would be expected for a mammal of its brain size. There is, therefore, nothing specifically unusual about the extent of the gyrencephaly observed in the extant elephant brain. ...
This study provides quantitative data on the extent of gyrencephaly in the large-brained African elephant and several species of cetaceans (from smaller to larger brained) in comparison with other mammals. Across three mammalian orders (primates, carnivores, and artiodactyls), the species with the larger brains are more gyrencephalic with each order, exhibiting a specific negative allometry. The African elephant, with a 5-kg brain, has a gyrencephalic index (GI) of 3.89, which, though highly gyrencephalic, is not more so than would be predicted for a mammal with a 5-kg brain. The cetaceans had an average GI of 5.43, are the most gyrencephalic mammals studied to date, and are more gyrencephalic than one would predict based on comparison with other mammals. No relationship between brain mass and GI was evident in the cetaceans as seen in other mammals, with all cetaceans showing similar GIs irrespective of brain mass (range of GI 5.23-5.70, range of brain mass 577-5617 g). This is yet another parameter indicating cetaceans to be neuroanatomical outliers. Two species of pinnipeds studied had GIs that were well above those seen for terrestrial carnivores, and the aquatic manatee was close to lissencephalic. Thus, all three groups of marine mammals showed unusual extents of cortical gyrencephaly, indicating a morphological alteration of the telencephalon associated with the return to the marine environment. The analysis suggests that cortical thickness and neuronal density are important factors in determining the extent of gyrencephaly across mammalian species.
... Nevertheless, despite elephants' status as the largest living terrestrial mammal, very little is known about the brain of this species. Prior to 2001, only a few original articles had specifically focused on the elephant central nervous system (Cozzi et al. 2001). Although the gross anatomy of the *5 kg adult elephant brain has been investigated in the last decade (Kupsky et al. 2001; Hakeem et al. 2005 Hakeem et al. , 2009 Shoshani et al. 2006; Manger et al. 2010), virtually nothing is known about the microstructural morphology of its neurons. ...
... Indeed, until recently, the only apparent insight into elephant cortical neuromorphology was a single camera lucida drawing from an Indian elephant (Elephas maximus; Barasa and Shochatovitz 1961 ). Reasons for this poverty of data are many (Cozzi et al. 2001), but include a propensity for neuroscientists to focus on the rodent and primate species commonly used in biomedical research (Manger et al. 2008), and a lack of well-preserved elephant brain tissue suitable for histological analysis. This latter issue was recently addressed by Manger et al. (2009), who were able to fix the brains of wild African elephants (Loxodonta africana) by postmortem, carotid cannulationperfusion . ...
Virtually nothing is known about the morphology of cortical neurons in the elephant. To this end, the current study provides the first documentation of neuronal morphology in frontal and occipital regions of the African elephant (Loxodonta africana). Cortical tissue from the perfusion-fixed brains of two free-ranging African elephants was stained with a modified Golgi technique. Neurons of different types (N=75), with a focus on superficial (i.e., layers II-III) pyramidal neurons, were quantified on a computer-assisted microscopy system using Neurolucida software. Qualitatively, elephant neocortex exhibited large, complex spiny neurons, many of which differed in morphology/orientation from typical primate and rodent pyramidal neurons. Elephant cortex exhibited a V-shaped arrangement of bifurcating apical dendritic bundles. Quantitatively, the dendrites of superficial pyramidal neurons in elephant frontal cortex were more complex than in occipital cortex. In comparison to human supragranular pyramidal neurons, elephant superficial pyramidal neurons exhibited similar overall basilar dendritic length, but the dendritic segments tended to be longer in the elephant with less intricate branching. Finally, elephant aspiny interneurons appeared to be morphologically consistent with other eutherian mammals. The current results thus elaborate on the evolutionary roots of Afrotherian brain organization and highlight unique aspects of neural architecture in elephants.
... Elephants have the largest absolute brain size of any land animal: 5.5 kg in Asian elephants and 6.5 kg in African savannah elephants (16)(17)(18). These values are Ϸ4 times the average brain mass of humans (9,19). ...
... Furthermore, several lines of indirect evidence suggest that the elephant neocortex is likely to require a great deal of energy on a neuron-specific basis. The elephant neocortex has a relatively low density of very largesized neurons (41,42) with extensive dendritic arborization (16), suggesting that each receives a relatively large number of synapses from interconnecting axons as compared with a large-brained primate (43). Accordingly, the interneuronal space in the elephant neocortex is occupied by a remarkably high density of glial cells (42). ...
Specific sets of brain-expressed genes, such as aerobic energy metabolism genes, evolved adaptively in the ancestry of humans and may have evolved adaptively in the ancestry of other large-brained mammals. The recent addition of genomes from two afrotherians (elephant and tenrec) to the expanding set of publically available sequenced mammalian genomes provided an opportunity to test this hypothesis. Elephants resemble humans by having large brains and long life spans; tenrecs, in contrast, have small brains and short life spans. Thus, we investigated whether the phylogenomic patterns of adaptive evolution are more similar between elephant and human than between either elephant and tenrec lineages or human and mouse lineages, and whether aerobic energy metabolism genes are especially well represented in the elephant and human patterns. Our analyses encompassed approximately 6,000 genes in each of these lineages with each gene yielding extensive coding sequence matches in interordinal comparisons. Each gene's nonsynonymous and synonymous nucleotide substitution rates and dN/dS ratios were determined. Then, from gene ontology information on genes with the higher dN/dS ratios, we identified the more prevalent sets of genes that belong to specific functional categories and that evolved adaptively. Elephant and human lineages showed much slower nucleotide substitution rates than tenrec and mouse lineages but more adaptively evolved genes. In correlation with absolute brain size and brain oxygen consumption being largest in elephants and next largest in humans, adaptively evolved aerobic energy metabolism genes were most evident in the elephant lineage and next most evident in the human lineage.
... They are bilaterally innervated by the proboscidean nerve, which is formed by the union of maxillary and facial nerve branches and runs along both sides of the proboscis (Boas & Paulli, 1908;Mariappa, 1986;Shoshani, 1997). It is assumed that the cortical representation of the trunk occupies a large area of the brain, although this remains unobserved (Cozzi, Spagnoli, & Bruno, 2001;Haug, 1970). ...
... The functional asymmetries of the anatomically symmetric trunk, reflected as side preferences, might indicate an anatomical asymmetry of the elephant's brain hemispheres, comparable with brain asymmetries described for other vertebrates (Bradshaw, 1989;Hopkins & Pilcher, 2001;Witelson, 1977). In elephants, neither has the representation of the trunk in the motor cortex been investigated sufficiently (Cozzi et al., 2001;Haug, 1970) nor has anything been mentioned about anatomical asymmetries of the brain. The cortex is highly structured with a folding index, which even exceeds the human one (Haug, 1969). ...
In this article, the side preferences of feeding-related trunk movements of free-ranging Asian elephants (Elephas maximus) were investigated for the first time. It is hypothesized that a functional asymmetry of the trunk is necessary to perform skillful feeding movements more efficiently. This might be connected with a corresponding hemispheric specialization. Video recordings of 41 wild elephants provided frequencies and durations of the following trunk-movement categories: object contact, retrieval, and reaching. In each category, individual side preferences were found. The strength of side preferences varied between the trunk-movement categories and the sexes. Mean durations of retrieval and reaching correlated negatively with the strength of side biases. Comparing the side preferences in the unpaired trunk with analogous phenomena in other unpaired grasping organs and in primate handedness. the authors discuss possible explanations for the evolution of asymmetries in unpaired grasping organs.
... Elephant brains (1,2) are functionally largely uncharted because of a lack of access to brains and the nonfeasibility of invasive mapping. We sought to break this barrier by a several decade collection effort, quantitative nerve tracing, comparative analysis, simple/robust staining methods, and detailed analysis of cell number, size, and position. ...
We studied facial motor control in elephants, animals with muscular dexterous trunks. Facial nucleus neurons (~54,000 in Asian elephants, ~63,000 in African elephants) outnumbered those of other land-living mammals. The large-eared African elephants had more medial facial subnucleus neurons than Asian elephants, reflecting a numerically more extensive ear-motor control. Elephant dorsal and lateral facial subnuclei were unusual in elongation, neuron numerosity, and a proximal-to-distal neuron size increase. We suggest that this subnucleus organization is related to trunk representation, with the huge distal neurons innervating the trunk tip with long axons. African elephants pinch objects with two trunk tip fingers, whereas Asian elephants grasp/wrap objects with larger parts of their trunk. Finger "motor foveae" and a positional bias of neurons toward the trunk tip representation in African elephant facial nuclei reflect their motor strategy. Thus, elephant brains reveal neural adaptations to facial morphology, body size, and dexterity.
... Both elephants and cetaceans possess all components of the basal ganglia found in other vertebrates (i.e., caudate, putamen, and globus pallidus) as this is a highly conserved system crucial for integrative functions (Oelschläger et al. 2008). These structures also show the typical mammalian topographic relationships to each other and to adjacent structures (Cozzi et al. 2001;Oelschläger and Oelschläger 2009). In cetaceans, the corpus striatum, involved in motor and reward systems, is prominent in size (Oelschläger et al. 2008) with a histological organization similar to that observed in other mammals (Oelschläger and Oelschläger 2009). ...
The present review assesses the potential neural impact of impoverished, captive environments on large-brained mammals, with a focus on elephants and cetaceans. These species share several characteristics, including being large, wide-ranging, long-lived, cognitively sophisticated, highly social, and large-brained mammals. Although the impact of the captive environment on physical and behavioral health has been well-documented, relatively little attention has been paid to the brain itself. Here, we explore the potential neural consequences of living in captive environments, with a focus on three levels: (1) The effects of environmental impoverishment/enrichment on the brain, emphasizing the negative neural consequences of the captive/impoverished environment; (2) the neural consequences of stress on the brain, with an emphasis on corticolimbic structures; and (3) the neural underpinnings of stereotypies, often observed in captive animals, underscoring dysregulation of the basal ganglia and associated circuitry. To this end, we provide a substantive hypothesis about the negative impact of captivity on the brains of large mammals (e.g., cetaceans and elephants) and how these neural consequences are related to documented evidence for compromised physical and psychological well-being.
... Along that line, substantial progress is noted in the study of brain structure in gyrencephalic species beyond primates, such as the dromedary (Simon, 1965), llama (Welker et al., 1976), horse (Cozzi et al., 2014), hippopotamus (Butti et al., 2014), rhinoceros (Manger, 2011;Bhagwandin et al., 2017), elephant seal, and sea lion (Sawyer et al., 2016;Turner et al., 2017), not to mention the extensive literature on proboscidea (Dexler, 1907;Jakob, 1909;Janssen and Stephan, 1956;Haug, 1966;Cozzi et al., 2001;Shoshani et al., 2006;Jacobs et al., 2011;Herculano-Houzel et al., 2014) and cetacea (Tower, 1954;Haug, 1970;Walløe et al., 2010;Butti et al., 2011;Mortensen et al., 2014). ...
... Elephantine intelligence and 'culture' (e.g., self recognition, special care for the dead, tool use) has long fascinated scientists (see Shoshani et al., 2006, andHart et al., 2007, for reviews). Studying the brain of elephants to understand how they produce their behavior has long been a fascinating task (Cozzi et al., 2001). However, the low diversity of present day Proboscidea (three species belonging to the single family Elephantidae) prevents comparative analyses of their central nervous system (Byrne and Bates, 2007). ...
Endocranial casts are the only available material to study the evolution of brain morphology through geologic time. However, these are not just casts of brain tissues but also include, e.g., meningeal tissues, blood vessels, and nerves. Tissues surrounding the brain are particularly thick in proboscideans, making the estimation of brain size in extinct proboscideans very tentative. Here the regression of brain mass over cranial capacity - based on data on intraindividual comparison between those two metrics in the literature - is used to used to estimate the 'true' brain mass of extinct mammals. This regression reveals that cranial capacity is allometrically related to brain mass in mammals. The larger the brain, the greater is the difference between brain mass and cranial capacity. Applied to proboscideans, this new method suggests that the thickness of non-neural tissues surrounding the brain has been greatly overestimated in extinct proboscidean species, resulting in the underestimation of brain mass. This data set suggests that a comparatively small brain is likely primitive for Proboscidea and that the representatives of the clade Elephantimorpha have inherited their large brain from their last common ancestor. The largest brain proportional to mass of all Proboscidea belongs to the Quaternary dwarf elephant of Sicily, which would have been comparable to modern humans in encephalization quotient.
... Once corrected for body size, the African elephant has a brain comparable in size and complexity to those of humans and other primates (Cozzi et al., 2001). This certainly contributes to the popular belief that elephants have exceptional brainpower. ...
... Primates, that have an expanded temporal lobe, appear to represent a derived condition of the relative location of major nuclear clusters within the amygdala. Given the expansion of the temporal lobe of the elephant (Cozzi et al. 2001), which is closely related to the rock hyrax, we would expect to see a differently oriented relationship among nuclear clusters within this species, perhaps similar to that seen in primates. ...
The current study details the nuclear organization of the rock hyrax amygdaloid complex using both Nissl and myelin stains, along with a range of immunohistochemical stains. The rock hyrax appears to be the least derived of the Afrotherians, a group with a huge range of body phenotypes, life histories and specialized behaviours, brain sizes, and ecological niches. In this sense, the rock hyrax represents a species where the organization of the amygdaloid complex may be reflective of that in stem Eutherian mammals. Our analysis indicates that the nuclear organization of the rock hyrax amygdaloid complex is indeed very similar to that in other mammals studied, with four major nuclear groupings (the deep or basolateral group; the superficial or cortical-like or corticomedial group; the centromedial group; and the other amygdaloid nuclei) being observed, which is typical of Eutherian mammals. Moreover, each of these groupings is composed of several nuclei, the vast majority of which were readily identified in the rock hyrax. Small nuclei identified in rodents and primates were absent in the superficial and centromedial groups, seemingly involved with olfaction. A novel shell-like nucleus of the accessory basal nuclear cluster was observed in the rock hyrax, again, likely to be involved in olfaction. The current study underlines the conserved nature of nuclear parcellation in the Eutherian mammal amygdaloid complex and indicates that across most species, the flow of information processing related to species-specific affective-laden stimuli and the resultant physiological and behavioural outcomes are likely to be similar across species.
... However, very few studies have been conducted on the gross morphology of the proboscidean brain. Cozzi et al. (2001) surveyed the literature on neuroanatomical data of proboscideans and found only 52 articles, 20 of which were written prior to 1900. Intact elephant brains are very difficult to acquire and prepare, which has hampered intensive study of the neuroanatomy of this species (Manger et al., 2009). ...
... The general brain morphology of the Yuka specimen resembles that observed in the modern elephants (Cozzi et al., 2001;Shoshani et al., 2006). The Yuka specimen demonstrates well-preserved dura mater (Fig. 1AeB) with its folds (falx cerebri, tentorium cerebelli, diaphragma sellae) and well-seen vessels and sinuses including sinus sagittalis superior and large lacunae (lacunae lateralis), amounting to 2*8 mm in the fixed material, sinus transverses, and the confluens sinuum (torcular of Herophili). ...
Abstract
This paper describes the treatment and results of the fixation procedure, extraction, dissection, and data collection of the preserved Late Pleistocene brain of the mummified specimen from permafrost. The partial carcass of the Woolly mammoth (Mammuthus primigenius (Blumenbach 1799)) nicknamed “Yuka” was found in 2010 on the Dmitrii Laptev Sea coast (Northern Yakutia, Russia). It dates to 39,440–38,850 cal. BP. This fossil presents the unique opportunity to study the preserved brain from permafrost, with well-defined major gross anatomy features of the cerebrum and cerebellum and internal structures revealed by Computed tomography (CT) and Magnetic resonance imaging (MRI). Anatomical description, CT data including volumetry, and results of the histological and electron microscopy study of the specimen are provided.
Keywords
Brain; Permafrost; Late Pleistocene; Yuka Woolly mammoth
... Tab. 4 -Brain weight (g), body weight (kg) and EQ of selected mammalian species. -Houzel et al., 2014; for analysis of older gray literature see Cozzi et al., 2001) for the lateral development of the temporal lobes and the general outline of the telencephalon, but the reciprocal position of the telencephalon and cerebellum of Physeter macrocephalus is quite unique. Comparisons with the brain of a fin whale (Balaenoptera physalus (Linnaeus, 1758)) of corresponding length, also maintained at the MMMTB (data not shown), indicate that the brain of P. macrocephalus is indeed heavier and larger, a fact often reported in the literature (for a general review see Marino, 2002). ...
The sperm whale (Physeter macrocephalus, Linnaeus 1758) possesses the largest brain that ever existed. Relatively few authors have dealt with it and the available descriptions are heterogeneous, with only few data about brain weight or gross anatomy. In fact the central nervous system of large cetaceans is quite difficult to obtain, given the huge body size and the low frequency of strandings of recently dead individuals. Furthermore, since the skull of the sperm whale underwent an extreme transformation for the accommodation of the spermaceti organ, the cranial cavity is surrounded by thick layers of bone and thus difficult to reach under field conditions.
We recently had the chance to extract the brain from two stranded sperm whales whose bodies were in good condition. In the present note we describe the main macroscopic characteristics of the sperm whale brain, including its weight and Encephalization Quotient, review the available literature, and describe a possible new approach to the removal and preservation of the organ under field conditions.
... The elephant genome may provide insights into some aspects of human evolution. Elephants are one of the few mammalian lineages in which large brains evolved (24,76,77). One genomic study compared genes under selection in the lineage leading to humans (from mice to nonhuman primates to humans) to genes under selection in the lineage leading from tenrec to elephant (78). ...
We review DNA-based studies of elephants and recently extinct proboscideans. The evidence indicates that little or no nuclear gene flow occurs between African savanna elephants (Loxodonta africana) and African forest elephants (Loxodonta cyclotis), establishing that they comprise separate species. In all elephant species, males disperse, whereas females remain with their natal social group, leading to discordance in the phylogeography of nuclear and mitochondrial DNA patterns. Improvements in ancient DNA methods have permitted sequences to be generated from an increasing number of proboscidean fossils and have definitively established that the Asian elephant (Elephas maximus) is the closest living relative of the extinct woolly mammoth (Mammuthus primigenius). DNA-based methods have been developed to determine the geographic provenance of confiscated ivory in an effort to aid the conservation of elephants. Expected final online publication date for the Annual Review of Animal Biosciences Volume 3 is February 15, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
... Due to the importance of the innervation of the proboscis, the area covered by the facial nerve is immensely much larger in elephants than in mammals not possessing a proboscis, which is clearly indicated by the expansion of its nucleus with large neurons and its huge root (Verhaart, 1962: p. 512;Cozzi et al., 2001). Thus, tapirs, which have developed a mobile proboscis akin to that of elephants, but shorter and not nearly as useful, also have a remarkably large facial nerve (Boas and Paulli, 1908: Pl. 7;Witmer et al., 1999: Fig. 2A, 4). ...
... Due to the difficulty to obtain the complete elephant's brain, very few articles reported on its anatomy. Most of the description and conclusion reported in comparative study relying on second hand data (Cozzi et al., 2001) and only specific parts of the brain. Haug (1987) estimated the macroscopic size of brain and cortex. ...
Cranial dura mater of two dying male Asian elephants (Elephas maximus) aged 24 years and 68 years were performed for gross and microscopic studied. The cranial dura mater consisted of two layers, outer periosteal layer and inner meningeal layer. Porous appearance forming by blood vessels were seen between the two layers. Some completed foramens were found in falx cerebri sheet. Unlike most of domestic animals, there were two falx cerebelli running along two sides of vermis and also many small tubercles on the surface of inner meningeal layer. By staining with Hematoxylin & Eosin, Masson Trichrome and Weigert stains, these small tubercles were collagenous mass protrusion.
... Elephants are large-brained, intelligent and inquisitive animals (Rensch 1956(Rensch , 1957Shoshani & Eisenberg 1992;Poole 1998;Roth 1999;Cozzi, Spagnoli & Bruno 2001;Hart, Hart, McCoy & Sarath 2001;Hakeem, Hof, Sherwood, Switzer et al. 2005; Douglas-Hamilton, Bhalla, Wittemyer & Vollrath 2006;Plotnik, de Waal & Reiss 2006;Shoshani, Kupsky & Marchant 2006;Poole & Moss 2008); we only need watch the tip of an elephant's trunk, the posture of its ears and the angle of its head to gain a window into its actively engaged mind. In the wild, everything elephants do is an intellectual challenge: locating and manipulating a wide variety of food items; remembering the location of water during a drought; searching for potential mates; deciding where to go, who to go with, who to join and who to avoid. ...
... The current study has, for the first time in over 50 years [Cozzi et al., 2001], provided a comprehensive framework detailing the anatomical organization of the African elephant diencephalon and brainstem. The analysis provided here has shown that specific aspects of the organization of these brain regions in the elephant have undergone a moderate amount of change, specifically those associated with the timing aspects of the motor systems, the production and reception of vocalizations, the satiety and sleep-wake systems, and the potential neurogenic lining of much of the ventricular surface in the brainstem. ...
The current study examined the organization of the diencephalon and brainstem of the African elephant (Loxodonta africana) - a region of the elephant brain that has not been examined for at least 50 years. The current description, employing material amenable for use with modern neuroanatomical methods, shows that, for the most part, the elephant diencephalon and brainstem are what could be considered typically mammalian, with subtle differences in proportions and topology. The variations from these previous descriptions, where they occurred, were related to four specific aspects of neural information processing: (1) the motor systems, (2) the auditory and vocalization systems, (3) the orexinergic satiety/wakefulness centre of the hypothalamus and the locus coeruleus, and (4) the potential neurogenic lining of the brainstem. For the motor systems, three specific structures exhibited interesting differences in organization - the pars compacta of the substantia nigra, the facial motor nerve nucleus, and the inferior olivary nuclear complex, all related to the timing and learning of movements and likely related to the control of the trunk. The dopaminergic neurons of the substantia nigra appear to form distinct islands separated from each other by large fibre pathways, an appearance unique to the elephant. Each island may send topologically organized projections to the striatum forming a dopaminergic innervation mosaic that may relate to trunk movements. At least five regions of the combined vocalization production and auditory/seismic reception system were specialized, including the large and distinct nucleus ellipticus of the periaqueductal grey matter, the enlarged lateral superior olivary nucleus, the novel transverse infrageniculate nucleus of the dorsal thalamus, the enlarged dorsal column nuclei and the ventral posterior inferior nucleus of the dorsal thalamus. These specializations, related to production and reception of infrasound, allow the proposal of a novel concept regarding the reception and localization of infrasonic sources. The orexinergic system of the hypothalamus displayed a medial hypothalamic parvocellular cluster of neurons in addition to the magnocellular clusters typical of mammals located in the lateral hypothalamus, and a novel medial division of the locus coeruleus was observed in the pons. These systems are related to appetitive drive and promotion of wakefulness, two aspects of elephant behaviour that appear to be inextricably linked. Lastly, we observed an extensive potential neurogenic lining of the ventricles throughout the brainstem that is present in even quite old elephants, although the function of these cells remains elusive. These observations combined demonstrate that, while much of the elephant brainstem is typically mammalian, certain aspects of the anatomy related to specialized behaviour of elephants are present and instructive in understanding elephant behaviour. © 2013 S. Karger AG, Basel.
... Due to the importance of the innervation of the proboscis, the area covered by the facial nerve is immensely much larger in elephants than in mammals not possessing a proboscis, which is clearly indicated by the expansion of its nucleus with large neurons and its huge root (Verhaart, 1962: p. 512;Cozzi et al., 2001). Thus, tapirs, which have developed a mobile proboscis akin to that of elephants, but shorter and not nearly as useful, also have a remarkably large facial nerve (Boas and Paulli, 1908: Pl. 7;Witmer et al., 1999: Fig. 2A, 4). ...
The dinosaur Diplodocus has a single, relatively large external bony narial orifice that is positioned far back between the orbits. In some mammals, such as elephants and tapirs, the caudal position of the narial opening is associated with a proboscis, so it has been suggested that Diplodocus possibly also had a trunk. In elephants, the facial nerve is large as it emerges from the brain. A branch of this nerve and a branch of the trigeminal nerve unite to form the proboscidial nerve that supplies the muscles of the powerful and complex motor system of the trunk. In contrast to the situation in modern elephants, the absolute as well as the relatively small size of the facial nerve in Diplodocus (deduced from an endocranial cast) indicates that there is no paleoneuroanatomical evidence for the presence of an elephant-like proboscis in this genus.
... 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 . ...
The current paper details our developing understanding of the evolution of large brains in mammals. In order to do this, we first define brains that we consider to be large – those that have passed the apparent 700-gram ceiling on brain mass evolution in the class Mammalia. The over-700-gram club includes certain species within the genus Homo, order Cetacea, order Proboscidea, and suborder Pinnipedia. Our analysis suggests that selection for body size appears to be the most important factor in the evolution of large brain size, but there also appear to be internal morphophysiological constraints on large brain size evolution that need to be overcome in order for brains to break the 700-gram barrier. These two aspects appear to be common themes in the evolution of large brains. This significantly diminishes the explanatory value of selection for greater cognitive capacities as a principal factor in the evolution of enlarged brain sizes above the 700-gram threshold.
... Under the layer of meninx, the neopallium of extant elephants ( Elephas and Loxodonta ) is densely sulcated. Past workers have recognized a deep sylvian fossa, an arched suprasylvia and a coronolateral (or lateral) sulcus, just as in Hyracoidea, but failed to identify a splenial sul- cus in most cases [Elliot Smith, 1902;Friant, 1954aFriant, , b, 1957Anthony, 1972;Cozzi et al., 2001;Shoshani et al., 2006]. In addition they found a sylvian fossa prolongated dorsally by a deep pseudosylvia , a praesylvian sulcus starting from the anterior rhinal fissure and bearing three ramifications, a transverse sulcus called the fissure of Rolando, an antero-temporal sulcus called the postsylvia and a postero-temporal sulcus called the sulcus postlateral. ...
Virtually reconstructed and natural endocranial casts are used in the study of brain evolution through geological time. We here present work investigating the paleoneurological evolution of afrotherian mammals. Using microCT-generated endocasts we show that, with the exception of the subfamilies Macroscelidinae and Tenrecoidea, most Afroinsec-tiphilia display a more or less gyrencephalic and ventrally expanded neopallium, two derived features that are unexpected for these insectivore-grade afrotherians. This implies that the endocranial cast morphology at the root of the afrotherian clade may have been more advanced than previously thought. The reconstructed endocranial morphology of the Afrotheria's last common ancestor reaches the level of complexity of some early Cenozoic archaic ungulates. Our result gives support to the hypothesis of an ungulate-like ancestral body plan for Afrotheria. It also implies that the a priori 'primitive' suite of traits evident in the brain of Afroinsectivora, especially in the tenrecs, may have been secondarily acquired. Implications on the overestimation of the divergence age of Afrotheria are discussed.
... The African elephant possesses three cell layers as is typical of other mammals and as reported previously for the elephant [for review see Cozzi et al., 2001]. The layers include the outermost molecular layer, in which the inhibitory interneurons classified as basket cells and stellate cells were located, the Purkinje cell layer with large cell bodies forming a lamina of a single cell's width, underneath which a cell-sparse lamina was observed, and the innermost granule cell layer that contained densely packed granule cells, Golgi type II cells, Lugaro cells and unipolar brush cells (fig. 3 ). ...
The current study provides a number of novel observations on the organization and structure of the cerebellar cortex of the African elephant by using a combination of basic neuroanatomical and immunohistochemical stains with Golgi and stereologic analysis. While the majority of our observations indicate that the cerebellar cortex of the African elephant is comparable to other mammalian species, several features were unique to the elephant. The three-layered organization of the cerebellar cortex, the neuronal types and some aspects of the expression of calcium-binding proteins were common to a broad range of mammalian species. The Lugaro neurons observed in the elephant were greatly enlarged in comparison to those of other large-brained mammals, suggesting a possible alteration in the processing of neural information in the elephant cerebellar cortex. Analysis of Golgi impregnations indicated that the dendritic complexity of the different interneuron types was higher in elephants than other mammals. Expression of parvalbumin in the parallel fibers and calbindin expressed in the stellate and basket cells also suggested changes in the elephant cerebellar neuronal circuitry. The stereologic analysis confirmed and extended previous observations by demonstrating that neuronal density is low in the elephant cerebellar cortex, providing for a larger volume fraction of the neuropil. With previous results indicating that the elephants have the largest relative cerebellar size amongst mammals, and one of the absolutely largest mammalian cerebella, the current observations suggest that the elephants have a greater volume of a potentially more complexly organized cerebellar cortex compared to other mammals. This quantitatively larger and more complex cerebellar cortex likely represents part of the neural machinery required to control the complex motor patterns involved in movement of the trunk and the production of infrasonic vocalizations.
... Our knowledge on elephant brain anatomy and physiology has increased tremendously in the past few years. Cozzi et al. (2001) summarized the available literature they could find and stated that many writers cited papers on brains of elephants from second hand data of old papers dating to the XIX century. Based on dissections and histological examinations of African and Asian elephant brains, Kupsky et al. (2001) provided illustrations to show the location of t ...
With the addition of 13 new taxa, we recognized 175 species and subspecies of proboscideans, classified in 42 genera and 10 families. The three extant species are: forest African elephant (Loxodonta cyclotis), bush African elephant (L. africana), and Asian elephant (Elephas maximus, with three subspecies). Rigorous analysis of characters published or awaiting publication is imperative for better understanding of the cladistic relationships among currently recognized proboscideans. Here we focus on “aquatic ancestry” of Proboscidea, interordinal relationships within Placentalia, proboscidean taxonomy in general and South American in particular, anatomy and physiology and some ecological considerations. New taxa above the family level include sister taxa Mammutida and Elephantida, and Plesielephantiformes as a sister taxon to Elephantiformes. Neontological research is currently under way on the hyoid apparatus, lungs, brain, hearing, ecology and behavior. Topics for future research include: phylogenetic positions of anthracobunids, Moeritherium, tetralophodont gomphotheres, Stegolophodon and Stegodon, and intra-familial relationships among Loxodonta, Elephas and Mammuthus, and continuing studies on encephalization quotient. Certain anatomical features and functions (e.g., the hyoid apparatus that helps in food procurement, in production of infrasonic sounds, and in storing water to be used in time of stress) evolved about 25 million years ago, in time for diversification into new niches when grasses appeared in the landscape.
... The few studies available on the gross anatomy and structure of the cerebral cortex of elephants 65 highlight a gyral complexity that is second only to cetaceans and includes an expanded neocortex with enlarged temporal, frontal, insular, parietal, cingulate, and hippocampal cortices, but with a poor development of the occipital cortex. 66 A recent study that examined the neuronal morphology of pyramidal neurons in the superficial layers of frontal and occipital cortices of the African elephant highlighted differences between this species, primates, and rodents, including dendritic length, branching patterns, and orientation. ...
The evolutionary process of readaptation to the aquatic environment was accompanied by extreme anatomical and physiological changes in the brain. This review discusses cortical specializations in the three major lineages of marine mammals in comparison to related terrestrial and semiaquatic species. Different groups of marine mammals adopted a wide range of strategies to cope with the challenges of aquatic living. Cetaceans and hippopotamids possess a completely agranular neocortex in contrast to phocids and sirenians; vertical modules are observed in deep layers V and VI in manatees, cetaceans, phocids, and hippopotamids, but in different cortical areas; and clustering in layer II appears in the insular cortex of hippopotamids, phocids, and cetaceans. Finally, von Economo neurons are present in cetaceans, hippopotamids, sirenians, and some phocids, with specific, yet different, cortical distributions. The interpretation of the evolutionary and functional significance of such specializations, and their relationships with the degrees of adaptation to the aquatic environment and phylogeny, remain difficult to trace, at least until comprehensive data, including representative species from all of the major mammalian families, become available.
... Previous investigations of neocortical organization in xenarthrans and afrotherians include electrophysiological studies of functional localization in the nine-banded armadillo (Dom et al. 1971;Royce et al. 1975), two-toed sloth (Meulders et al. 1966), three-toed sloth (De Moraes et al. 1963;Saraiva and Magalhães-Castro 1975), Madagascan lesser hedgehog tenrec (Krubitzer et al. 1997), and Cape elephant shrew (Dengler-Crish et al. 2006). In addition, there are reports of cortical architecture and parcellation in armadillos (Dom et al. 1971;Ferrari et al. 1998;Royce et al. 1975), the two-toed sloth , Madagascan lesser hedgehog tenrec (Schmolke and Künzle 1997), manatee (Marshall and Reep 1995;Reep et al. 1989;Sarko and Reep 2007), and elephant (Cozzi et al. 2001). None of these studies, however, provide detailed descriptions of the distribution of cellular types in the neocortex as defined by immunohistochemical staining patterns. ...
Interpreting the evolution of neuronal types in the cerebral cortex of mammals requires information from a diversity of species. However, there is currently a paucity of data from the Xenarthra and Afrotheria, two major phylogenetic groups that diverged close to the base of the eutherian mammal adaptive radiation. In this study, we used immunohistochemistry to examine the distribution and morphology of neocortical neurons stained for nonphosphorylated neurofilament protein, calbindin, calretinin, parvalbumin, and neuropeptide Y in three xenarthran species-the giant anteater (Myrmecophaga tridactyla), the lesser anteater (Tamandua tetradactyla), and the two-toed sloth (Choloepus didactylus)-and two afrotherian species-the rock hyrax (Procavia capensis) and the black and rufous giant elephant shrew (Rhynchocyon petersi). We also studied the distribution and morphology of astrocytes using glial fibrillary acidic protein as a marker. In all of these species, nonphosphorylated neurofilament protein-immunoreactive neurons predominated in layer V. These neurons exhibited diverse morphologies with regional variation. Specifically, high proportions of atypical neurofilament-enriched neuron classes were observed, including extraverted neurons, inverted pyramidal neurons, fusiform neurons, and other multipolar types. In addition, many projection neurons in layers II-III were found to contain calbindin. Among interneurons, parvalbumin- and calbindin-expressing cells were generally denser compared to calretinin-immunoreactive cells. We traced the evolution of certain cortical architectural traits using phylogenetic analysis. Based on our reconstruction of character evolution, we found that the living xenarthrans and afrotherians show many similarities to the stem eutherian mammal, whereas other eutherian lineages display a greater number of derived traits.
The Mediterranean monk seal ( Monachus monachus , Hermann, 1779) is an endangered species of pinniped endemic to few areas of the Mediterranean Sea. Extensive hunting and poaching over the last two centuries have rendered it a rare sight, scattered mainly in the Aegean Sea and the western coast of North Africa. In a rare event, a female monk seal calf stranded and died in southern Italy (Brindisi, Puglia). During due necropsy, the brain was extracted and fixed. The present report is the first of a monk seal brain. The features reported are remarkably typical of a true seal brain, with some specific characteristics. The brain cortical circonvolutions, main fissures and the external parts are described, and an EQ was calculated. Overall, this carnivore adapted to aquatic life shares some aspects of its neuroanatomy and physiology with other seemingly distant aquatic mammals.
The recent elephant species, the African savannah, the African forest, and the Asian elephant, are all social, and intraspecific communication is highly developed. Specifically, acoustic signals play a fundamental role within elephant societies. In this chapter, I have provided an overview of elephant communication with an emphasis on the African savannah and the Asian elephant’s vocal systems, discussing the acoustic structure of calls (sonic and infrasonic), sound production, and perception mechanisms. Behavioral correlates of endocrine mechanisms and regulations are reviewed using “musth” (a condition in bull elephants characterized by increased aggressive behavior and elevated androgen levels) as an example. Recent neuroanatomical studies in relation to vocal production and perception and the examples of vocal production learning are further discussed. The reader shall understand that the combination of behavioral, physiological, and neuroanatomical studies needs to be emphasized to understand the vocal capacities of these highly iconic and endangered species.
Xenarthra is one of the basal placental superclades. Xenarthra is approximately 100 million years old and includes armadillos, anteaters, and sloths. Xenarthrans share unique features including supplementary intervertebral articulations, internal testes, and low metabolic rates. Xenarthran neocortex shares a common organizational plan with all other mammals, but in some species, the somatomotor arrangement is unique, possibly representing an evolutionary intermediate between marsupials (eg, opossums) and Boreoeutheria (eg, felines, primates). The cortical laminae of xenarthrans are not as defined as in other clades. In all xenarthrans examined, striking modular features in layer II of cortex occupy a great extent of neocortex.
Comparative neuroanatomical studies have contributed substantial information about the brains of large mammals and expanded our understanding of cortical organization among species. In this chapter, we review some features of the largest extant mammals and include, where evidence is available, details about the organization and characteristics of the cerebral cortex, neuron morphology, subcortical structures, and cerebellum. We conclude with a brief discussion of putative cognitive and behavioral specializations associated with these species.
In the last decade clear evidence has accumulated that elephants are capable of vocal production learning. Examples of vocal imitation are documented in African (Loxodonta africana) and Asian (Elephas maximus) elephants, but little is known about the function of vocal learning within the natural communication systems of either species. We are also just starting to identify the neural basis of elephant vocalizations. The African elephant diencephalon and brainstem possess specializations related to aspects of neural information processing in the motor system (affecting the timing and learning of trunk movements) and the auditory and vocalization system. Comparative interdisciplinary (from behavioral to neuroanatomical) studies are strongly warranted to increase our understanding of both vocal learning and vocal behavior in elephants. article under the CC BY-NC-ND license (http://creative-commons.org/licenses/by-nc-nd/3.0/)
We report morphological data on brains of four African, Loxodonta africana, and three Asian elephants, Elephas maximus, and compare findings to literature. Brains exhibit a gyral pattern more complex and with more numerous gyri than in primates, humans included, and in carnivores, but less complex than in cetaceans. Cerebral frontal, parietal, temporal, limbic, and insular lobes are well developed, whereas the occipital lobe is relatively small. The insula is not as opercularized as in man. The temporal lobe is disproportionately large and expands laterally. Humans and elephants have three parallel temporal gyri: superior, middle, and inferior. Hippocampal sizes in elephants and humans are comparable, but proportionally smaller in elephant. A possible carotid rete was observed at the base of the brain. Brain size appears to be related to body size, ecology, sociality, and longevity. Elephant adult brain averages 4783g, the largest among living and extinct terrestrial mammals; elephant neonate brain averages 50% of its adult brain weight (25% in humans). Cerebellar weight averages 18.6% of brain (1.8 times larger than in humans). During evolution, encephalization quotient has increased by 10-fold (0.2 for extinct Moeritherium, ∼2.0 for extant elephants). We present 20 figures of the elephant brain, 16 of which contain new material. Similarities between human and elephant brains could be due to convergent evolution; both display mosaic characters and are highly derived mammals. Humans and elephants use and make tools and show a range of complex learning skills and behaviors. In elephants, the large amount of cerebral cortex, especially in the temporal lobe, and the well-developed olfactory system, structures associated with complex learning and behavioral functions in humans, may provide the substrate for such complex skills and behavior.
The hypothesis that independently of sex, brain volume (BV) and head circumference (HC) are positively and significantly associated with intellectual quotient (IQ) was examined in a sample of 96 high school graduates of high [Wechsler Intelligence Scale for Adults—Revised (WAIS-R)>120] and low IQ (WAIS-R<100) (1:1), from high and low socioeconomic stratum (SES), and of both sexes (1:1) from the Chile's metropolitan region. Brain development was assessed by magnetic resonance imaging (MRI) and anthropometric measurements were made applying standardized procedures. Results showed that, in general, no significant differences were observed between absolute and adjusted brain parameters by body size. Differences in BV and HC can be more properly attributed to differences in IQ and not to SES both in males and females. Independently of sex, BV was the only brain parameter that contributed to explain IQ variance. These findings confirm the hypothesis that independently of sex, BV and HC are positively and significantly associated with IQ.
Working with multi-species allometric relations and drawing on mammalian theorist Denenberg’s works, I provide an explanatory theory of the mammalian dual-brain as no prior account has.
Reptiles occupy a crucial position with respect to vertebrate phylogeny, having roamed the earth for more than 300 million years and given rise to both birds and mammals. To date, this group has been largely ignored by contemporary genomics technologies, although the green anole lizard was recently recommended for whole genome sequencing. Future experiments using flow-sorted chromosome libraries and high-throughout genomic sequencing will help to discover important findings regarding sex chromosome evolution, early events in sex determination, and dosage compensation. This information should contribute extensively toward a general understanding of the genetic control of development in amniotes.
Comparative genomics approaches are having a remarkable impact on the study of transcriptional regulation in eukaryotes. Many eukaryotic genome sequences are being explored by new computational methods and high-throughput experimental tools such as DNA arrays and genome-wide location analyses. These tools are enabling efficient panning for common regulatory cassettes underlying fundamental biological processes, extending the use of existing techniques for the discovery of response elements to mammals, deciphering the transcriptional regulatory code in eukaryotes and providing the first global insights into a recently described post-transcriptional regulatory mechanism. Collectively, these approaches are rapidly expanding both our knowledge and our definition of transcriptional regulation.
Only humans, chimpanzees, and orangutans have demonstrated that they recognize their reflections in mirrors. Other mammals (including over a dozen species of monkeys) have failed to show signs of self-recognition. Recent investigations have attempted to discover if the absence of self-recognition is related to a general inability to process mirrored information. This article describes the failure to find self-recognition in two adult Asian elephants (
Elephas maximus) along with their spontaneous use of mirrored information to locate otherwise hidden food. Ss responded appropriately on Trial 1 to novel placements of food items, but continued to respond to their images as if confronted by another elephant. Results are discussed in the context of the relationship (or lack thereof) between different types of mirror-mediated behavior and self-recognition. It is concluded that possession of mirror-mediated abilities is not a sufficient condition for the development of self-recognition. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Der Mensch ist in der Lage, durch seine geistige Leistungsfähigkeit seine Umwelt umzugestalten. Das können die Tiere nicht. Das Organ, das für die geistige Leistungsfähigkeit verantwortlich ist, ist das Gehirn. Es wäre daher zu erwarten, daß das menschliche Gehirn eine deutliche Sonderstellung innerhalb der Lebewesen besitzt. Bisher war es jedoch nicht möglich, morphologische Tat bestände im Gesamtaufbau des Gehirns zu finden, die die gegenüber den Tieren besonders hohe Intelligenz des Menschen hätten voll befriedigend erklären können. Um dies deutlich zu machen, sind in Tabelle 1 die Körper- und Gehirn gewichte von Säugetieren zusammengestellt, die die Situation exemplarisch be leuchten. Wir können uns auf die Säuger beschränken, da nur bei ihnen eine für höhere tierische Intelligenz entsprechende Gehirnentwicklung stattgefunden hat, und nur bei ihnen eine echte neocorticale Großhirnrinde entwickelt wurde. Für den Vergleich sind solche Arten ausgewählt worden, die innerhalb aller Mammalia oder ihrer Familien die größten und kleinsten Gehirne besitzen. Der Mensch hat mit einem mittleren Gehirngewicht von 1300--1500 g zwar ein großes Gehirn, aber es gibt Lebewesen, die größere Gehirne aufweisen. Von den land lebenden Tieren hat der Elefant ein etwa 3--4mal größeres Gehirn. Bei den \Valen gibt es eine ganze Anzahl von Arten, die ein höheres Gehirngewicht als der Mensch besitzen. Das größte Gehirn aller Lebewesen ist beim Pottwal zu finden; es erreicht knapp 10 kg (Jacobs und Jensen, 1964; Gihr und Pilleri, 1969b).
“Intelligent activity may reasonably be regarded as the key note of mammalian progress” (Romer 1962). This progress became possible with the acquisition of a neocortex, with its great analytic, associative and synthetic potential. Other mammalian characteristics, such as improvements in the circulation and in temperature regulation and, in most mammals, the long gestation period, giving birth to live young, and the development of nursing, with concomitant care and training of the young (Romer 1962), are conditional for the development, imprinting and functioning of a complicated brain. The main characteristics of the mammalian brain all are dependent on the presence of a neocortex.
Humanity and human intelligence are considered to be derived from the large human brain; therefore brain size is regarded as a relevant and interesting parameter. This chapter covers brain size in an evolutionary perspective. Such a starting point of course has an inherent limitation: attention is only paid to overall brain size, and not to the size of brain subsystems. Nevertheless, overall brain size is an interesting parameter.
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The following account of the anatomy of the head of a fœtal African Elephant was made possible by the acquisition of a single specimen, preserved immediately after extraction from the mother, who was shot in the Belgian Congo. As far as is known, this fœtus is the only well-preserved specimen in existence, the total number of fœtuses recorded since 1734 being twelve.
Apart from the skeleton, our knowledge of the anatomy of present-day Proboscideans is very meagre. The dissection hitherto carried out has been either a hasty study of the complete adult carcase, or a more lengthy observation of preserved portions of the animals. Both methods lead to inaccuracy, and provide an explanation of the numerous discrepancies in the accounts. When, therefore, the present Congo foetus was acquired by purchase from the Belgians who preserved it, and Professor D. M. S. WATSON kindly allowed me to have it for dissection, I determined to make the fullest possible use of this unique specimen. The dissection of the head was carried out under the Zeiss Binocular Dissecting Microscope, and sketches and photographs were prepared at intervals, so that every record should be kept.
Court, N. 1992 04 15: Cochlea anatomy ofNumidotherium koholense: auditory acuity in the oldest known proboscidean. Lethaia, Vol. 25, pp. 211–215. Oslo. ISSN 0024–1164.
A natural cast of the spiral cochlea space from the inner ear of the oldest known proboscidean, Numidotherium koholense, is described. The cast was sectioned to reveal internal structures. Cochlea structure in numiodtheres, and by inference auditory acuity, is shown to have been very different from that of living proboscideans. The cochlea of Numidotherium is deemed to reflect tuning to relatively high frequencies and contrasts with the low-frequency specializations seen in the inner ear of living proboscideans. It is suggested that evolution of the elephant otic region might be explained by a shift in developmental timing such that features occurring earlier in ontogeny are characteristic of the adult stage. *Proboscidea, Numidotherium, cochlea, natural cast, auditory acuity.
Observations were made on the eye of the living animal, 181 different species being examined, and frequently several individuals of the same species. The species comprise representatives of all the Mammalian orders except the Cetacea and Sirenia.
Reviews observations of elephant training in the field and in the zoo. Visual and auditory discriminations were learned. In comparative studies with an ass, a zebra, and a horse in the zoo, only the latter approximated the elephant's performance. Hypotheses regarding the relevance of brain characteristics as factors in learning and memory were offered. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
This chapter examines a series of ungulate brains that show a well-developed rhinencephalon in all forms. The sense of olfaction is important to all of them, although it may be of relatively less importance in those animals with the best developed brains, as there is not a proportionate increase in the rhinencephalic areas. The olfactory bulb and stalk is generally short and stocky, although in the bovine brain there is an elongation of both. Both medial and lateral olfactory tracts can be easily identified on the ventral surface, and what appears to be an intermediate olfactory tract is present in the elephant. The lateral olfactory gyrus, or prepiriform cortex, is quite prominent in all forms. With growth in the size of the brain and an increase in fissuration of the cortex, there is a corresponding increase in the fissures present in the lateral olfactory gyrus and in the hippocampal gyrus and the uncus. The wild goats and the springbuck show the least fissuration, the elephant the most. Increases in the total size of the brain are accompanied by an increase in the thickness of the cortex of the hippocampal gyrus overlying the inferior horn of the lateral ventricle and the hippocampal formation.
1.1. Brain lipids of intact baby mammoth and an adult mammoth from permafrost have been investigated. All glycerophospholipids were found to be desintegrated. But the sphingolipids remained nearly intact. The content of sphingomyelin was found to be equal to 14 mg per g dry weight. Eighteen fatty acids were detected in brain sphingomyelin, the main were stearic and nervonic acids.2.2. Cerebrosides and sulfocerebrosides were found in mammoth brain. The adult brain contained 44 mg of cerebrosides and 19 mg of sulfocerebrosides per g dry weight. These glycosphingolipids contain hydroxy and nonhydroxy long chain fatty acids. The long chain bases are represented by 4-sphingenine and to a smaller extent by sphinganine.3.3. Gangliosides were found in the brain of mammoths. Their concentration was low. ca. 700 mg sialic acid per g dry weight due to decomposition. The composition of gangliosides was restricted to monosialogangliosides GM1 (96.5%), GM2 and GM3 (3.5%).4.4. Cholesterol was detected in the brain of mammoths, with a content of ca. 102 mg per g dry weight. Cholesterol esters were also found.