3. "As large as you need and as small as you can": Implications of the brain size ofHomo floresiensis

2007 ◽  
pp. 35-42 ◽  
Author(s):  
Iain Davidson
Keyword(s):  
Brain Size ◽  
The Brain

scholarly journals Molecular evolutionary analysis of human primary microcephaly genes

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nashaiman Pervaiz ◽  
Hongen Kang ◽  
Yiming Bao ◽  
Amir Ali Abbasi
Keyword(s):  
Evolutionary History ◽  
Genetic Basis ◽  
Brain Size ◽  
Primate Species ◽  
Evolutionary Analysis ◽  
Australopithecus Afarensis ◽  
Primary Microcephaly ◽  
Modern Humans ◽  
History Of ◽  
The Brain

Abstract Background There has been a rapid increase in the brain size relative to body size during mammalian evolutionary history. In particular, the enlarged and globular brain is the most distinctive anatomical feature of modern humans that set us apart from other extinct and extant primate species. Genetic basis of large brain size in modern humans has largely remained enigmatic. Genes associated with the pathological reduction of brain size (primary microcephaly-MCPH) have the characteristics and functions to be considered ideal candidates to unravel the genetic basis of evolutionary enlargement of human brain size. For instance, the brain size of microcephaly patients is similar to the brain size of Pan troglodyte and the very early hominids like the Sahelanthropus tchadensis and Australopithecus afarensis. Results The present study investigates the molecular evolutionary history of subset of autosomal recessive primary microcephaly (MCPH) genes; CEP135, ZNF335, PHC1, SASS6, CDK6, MFSD2A, CIT, and KIF14 across 48 mammalian species. Codon based substitutions site analysis indicated that ZNF335, SASS6, CIT, and KIF14 have experienced positive selection in eutherian evolutionary history. Estimation of divergent selection pressure revealed that almost all of the MCPH genes analyzed in the present study have maintained their functions throughout the history of placental mammals. Contrary to our expectations, human-specific adoptive evolution was not detected for any of the MCPH genes analyzed in the present study. Conclusion Based on these data it can be inferred that protein-coding sequence of MCPH genes might not be the sole determinant of increase in relative brain size during primate evolutionary history.

scholarly journals Effects of Brain Size on Adult Neurogenesis in Shrews

2021 ◽  
Vol 22 (14) ◽  
pp. 7664
Author(s):  
Katarzyna Bartkowska ◽  
Krzysztof Turlejski ◽  
Beata Tepper ◽  
Leszek Rychlik ◽  
Peter Vogel ◽  
...  
Keyword(s):  
Adult Neurogenesis ◽  
Subventricular Zone ◽  
Molecular Mechanisms ◽  
Brain Size ◽  
Hippocampal Formation ◽  
Small Animals ◽  
Suncus Murinus ◽  
The Brain ◽  
Neomys Fodiens ◽  
Migratory Stream

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10–22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew’s brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.

On the anatomic relation of choroid plexus to brain: a comparative study

1980 ◽  
Vol 238 (1) ◽  
pp. R76-R81 ◽  
Author(s):  
H. F. Cserr ◽  
M. Bundgaard ◽  
J. K. Ashby ◽  
M. Murray
Keyword(s):  
Choroid Plexus ◽  
Brain Volume ◽  
Brain Size ◽  
Ventricular Volume ◽  
Brain Weight ◽  
Air Breathing ◽  
Original Proposal ◽  
Adaptive Value ◽  
Choroid Plexuses ◽  
The Brain

The size of choroid plexuses and cerebral ventricles relative to brain varies widely among vertebrates. The functional significance of this variability has attracted little attention since Herrick's original proposal that large choroid plexuses might enhance oxygen delivery to the brain and therefore be of adaptive value in the transition of vertebrates from water to air breathing. We compared choroid plexus and brain weight or ventricular and brain volume in 40 species from nine vertebrate groups. Both choroid plexus weight and ventricular volume were unrelated to brain size. Plexus weight ranged from 0 to 5.2% of brain weight and ventricular volume from 0.9 to 132% of brain volume. Amid this diversity the dipnoans, chondrosteans, holosteans, amphibians, and crossopterygian examined in this study are exceptional in uniformly having large plexuses. The adaptive significance of large choroid plexuses may lie in the presence of specific homeostatic mechanisms and their role in the response to the increases in PCO2 that accompany the transition to air breathing.

Longitudinal Brain Size Measurements in App/Ps1 Transgenic Mice

2010 ◽  
Vol 4 ◽  
pp. MRI.S5885 ◽  
Author(s):  
Trevor J. Vincent ◽  
Jonathan D. Thiessen ◽  
Laryssa M. Kurjewicz ◽  
Shelley L. Germscheid ◽  
Allan J. Turner ◽  
...  
Keyword(s):  
Brain Size ◽  
Three Dimensional ◽  
Gene Mutations ◽  
Mutant Form ◽  
Swedish Mutation ◽  
Significant Difference ◽  
Lateral Width ◽  
Resolution Imaging ◽  
Or Gene ◽  
The Brain

There appear to be species differences among the effects of gene mutations related to familial Alzheimer's disease on the brain during aging. To gain a better understanding of the effects of the Swedish mutation of amyloid precursor protein and the mutant form of human presenilin 1 on mice, commercially available mice from Jackson Laboratory were studied. Three dimensional T2*-weighted imaging was used to monitor the size of brains of APP/PS1 mice monthly, from 6 to 13 months of age. No significant difference was measured in the size of the medial-lateral width, dorsal-ventral height, rostral-caudal length or the volume of the APPSwe/ PS1 mouse brain. Faster and higher-resolution imaging methods are needed to accurately determine if small volume or shape changes occur in mouse brains with age or gene mutations.

scholarly journals Brain Size of the African Grasscutter (Thryonomys Swinderianus, Temminck, 1827) at Defined Postnatal Periods

2017 ◽  
Vol 61 (4) ◽  
pp. 5-11 ◽  
Author(s):  
C. S. Ibe ◽  
S. O. Salami ◽  
N. Wanmi
Keyword(s):  
Cognitive Ability ◽  
Brain Size ◽  
Natural Habitat ◽  
Brain Weight ◽  
Strong Positive Correlation ◽  
Positive Correlation ◽  
Thryonomys Swinderianus ◽  
Physiological Studies ◽  
The Difference ◽  
The Brain

Abstract As a sequel to the current advancement in ethology, this study was designed to provide information on the brain size of the African grasscutter at specific postnatal periods and to extrapolate these findings to the behaviour of the rodent in its natural habitat. Brain samples were extracted from African grasscutter neonates on postnatal day 6, juveniles on postnatal day 72 and adults on postnatal day 450 by basic neuro-anatomical techniques. The weight, volume and dimensions of the brain samples were determined in absolute and relative terms. Their encephalisation quotient was also computed. There was a very strong positive correlation between nose-rump length and brain length in the neonates. The relative brain weight of neonates, juveniles and adults were 3.84 ± 0.12 %, 2.49 ± 0.07 % and 0.44 ± 0.03 %, respectively. The differences were significant (P < 0.05). The encephalisation quotient of juveniles was 1.62 ± 0.03 while that of the adult was 0.49 ± 0.02. The difference was significant (P < 0.05). The results were extrapolated to the animal’s cognitive ability, and compared with other rodents. It was concluded that the juvenile African grasscutter may have higher cognitive ability than the adult rodent, thus, juveniles should be preferred in physiological studies of memory and cognition.

Brain size/body weight in the dingo (Canis dingo): comparisons with domestic and wild canids

2017 ◽  
Vol 65 (5) ◽  
pp. 292 ◽  
Author(s):  
Bradley P. Smith ◽  
Teghan A. Lucas ◽  
Rachel M. Norris ◽  
Maciej Henneberg
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Cuon Alpinus ◽  
Size Relationship ◽  
Wild Canids ◽  
Free Ranging ◽  
The Impact ◽  
Endocranial Volume ◽  
The Brain

Endocranial volume was measured in a large sample (n = 128) of free-ranging dingoes (Canis dingo) where body size was known. The brain/body size relationship in the dingoes was compared with populations of wild (Family Canidae) and domestic canids (Canis familiaris). Despite a great deal of variation among wild and domestic canids, the brain/body size of dingoes forms a tight cluster within the variation of domestic dogs. Like dogs, free-ranging dingoes have paedomorphic crania; however, dingoes have a larger brain and are more encephalised than most domestic breeds of dog. The dingo’s brain/body size relationship was similar to those of other mesopredators (medium-sized predators that typically prey on smaller animals), including the dhole (Cuon alpinus) and the coyote (Canis latrans). These findings have implications for the antiquity and classification of the dingo, as well as the impact of feralisation on brain size. At the same time, it highlights the difficulty in using brain/body size to distinguish wild and domestic canids.

Evolution of vertebrate brain size is associated with sexual traits

2020 ◽  
Vol 70 (4) ◽  
pp. 401-416
Author(s):  
Mao Jun Zhong ◽  
Long Jin ◽  
Jian Ping Yu ◽  
Wen Bo Liao
Keyword(s):  
Sexual Size Dimorphism ◽  
Brain Size ◽  
Finite Energy ◽  
Energy Resources ◽  
Testis Size ◽  
Vertebrate Brain ◽  
Sexual Traits ◽  
The Relationship ◽  
The Brain ◽  
Expensive Tissue Hypothesis

Abstract The expensive tissue hypothesis predicts a trade-off between investments in the brain and other energetically costly organs due to the costs associated with their growth and maintenance within the finite energy resources available. However, few studies address the strength of relationships between brain size and investments in precopulatory (ornaments and armaments) and postcopulatory (testes and ejaculates) sexual traits. Here, in a broad comparative study, we tested the prediction that the relationship between brain size and investment in sexual traits differs among taxa relative to the importance of sperm competition within them. We found that brain size was negatively correlated with sexual size dimorphism (SSD) in anurans and primates, and it tended to decrease with SSD in ungulates and cetaceans. However, brain size did not covary significantly with armaments (e.g., canine length, horn, antler, and muscle mass). Brain size was not correlated with postcopulatory sexual traits (testes and ejaculates). The intensity of covariance between brain size and precopulatory sexual traits decreased with increasing relative testis size.

scholarly journals Do Different Methods Yield Equivalent Estimations of Brain Size in Birds?

2020 ◽  
Vol 95 (2) ◽  
pp. 113-122
Author(s):  
Diego Ocampo ◽  
César Sánchez ◽  
Gilbert Barrantes
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Brain Mass ◽  
Wide Range ◽  
Evolutionary Studies ◽  
Relative Brain Size ◽  
Using Data ◽  
Endocranial Volume ◽  
The Brain ◽  
Size Estimates

The ratio of brain size to body size (relative brain size) is often used as a measure of relative investment in the brain in ecological and evolutionary studies on a wide range of animal groups. In birds, a variety of methods have been used to measure the brain size part of this ratio, including endocranial volume, fixed brain mass, and fresh brain mass. It is still unclear, however, whether these methods yield the same results. Using data obtained from fresh corpses and from published sources, this study shows that endocranial volume, mass of fixed brain tissue, and fresh mass provide equivalent estimations of brain size for 48 bird families, in 19 orders. We found, however, that the various methods yield significantly different brain size estimates for hummingbirds (Trochilidae). For hummingbirds, fixed brain mass tends to underestimate brain size due to reduced tissue density, whereas endocranial volume overestimates brain size because it includes a larger volume than that occupied by the brain.

scholarly journals The evolution of complex brains and behaviors in African cichlid fishes

2010 ◽  
Vol 56 (1) ◽  
pp. 144-156 ◽  
Author(s):  
Caroly A. Shumway
Keyword(s):  
Visual Acuity ◽  
Social Organization ◽  
Habitat Complexity ◽  
Brain Size ◽  
Brain Structures ◽  
Cichlid Fishes ◽  
African Cichlid ◽  
Monogamous Species ◽  
And Behavior ◽  
The Brain

Abstract In this review, I explore the effects of both social organization and the physical environment, specifically habitat complexity, on the brains and behavior of highly visual African cichlid fishes, drawing on examples from primates and birds where appropriate. In closely related fishes from the monophyletic Ectodinii clade of Lake Tanganyika, both forces influence cichlid brains and behavior. Considering social influences first, visual acuity differs with respect to social organization (monogamy versus polygyny). Both the telencephalon and amygdalar homologue, area Dm, are larger in monogamous species. Monogamous species are found to have more vasotocin-immunoreactive cells in the preoptic area of the brain. Habitat complexity also influences brain and behavior in these fishes. Total brain size, telencephalic and cerebellar size are positively correlated with habitat complexity. Visual acuity and spatial memory are enhanced in cichlids living in more complex environments. However habitat complexity and social forces affect cichlid brains differently. Taken together, our field data and plasticity data suggest that some of the species-specific neural effects of habitat complexity could be the consequence of the corresponding social correlates. Environmental forces, however, exert a broader effect on brain structures than social ones do, suggesting allometric expansion of the brain structures in concert with brain size and/or co-evolution of these structures.

scholarly journals Concentrations of Essential Trace Metals in the Brain of Animal Species—A Comparative Study

2020 ◽  
Vol 10 (7) ◽  
pp. 460 ◽  
Author(s):  
Chiara Alessia DeBenedictis ◽  
Andrea Raab ◽  
Ellen Ducie ◽  
Shauna Howley ◽  
Joerg Feldmann ◽  
...  
Keyword(s):  
Nervous System ◽  
Trace Metals ◽  
Trace Metal ◽  
Metal Content ◽  
Brain Size ◽  
Physiological Role ◽  
Physiological Concentration ◽  
Specific Distribution ◽  
Trace Metal Content ◽  
The Brain

The essential trace metals iron, zinc, and copper have a significant physiological role in healthy brain development and function. Especially zinc is important for neurogenesis, synaptogenesis, synaptic transmission and plasticity, and neurite outgrowth. Given the key role of trace metals in many cellular processes, it is important to maintain adequate levels in the brain. However, the physiological concentration of trace metals, and in particular zinc, in the human and animal brain is not well described so far. For example, little is known about the trace metal content of the brain of animals outside the class of mammals. Here, we report the concentration of iron, zinc, and copper in fresh brain tissue of different model-species of the phyla Chordata (vertebrates (mammals, fish)), Annelida, Arthropoda (insects), and Mollusca (snails), using inductively coupled plasma mass-spectrometry (ICP-MS). Our results show that the trace metals are present in the nervous system of all species and that significant differences can be detected between species of different phyla. We further show that a region-specific distribution of metals within the nervous system already exists in earthworms, hinting at a tightly controlled metal distribution. In line with this, the trace metal content of the brain of different species does not simply correlate with brain size. We conclude that although the functional consequences of the controlled metal homeostasis within the brain of many species remains elusive, trace metal biology may not only play an important role in the nervous system of mammals but across the whole animal kingdom.

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