scholarly journals Evidence for Concerted and Mosaic Brain Evolution in Dragon Lizards

2017 ◽  
Vol 90 (3) ◽  
pp. 211-223 ◽  
Author(s):  
Daniel Hoops ◽  
Marta Vidal-García ◽  
Jeremy F.P. Ullmann ◽  
Andrew L. Janke ◽  
Timothy Stait-Gardner ◽  
...  
Keyword(s):  
Body Size ◽  
Critical Role ◽  
Brain Evolution ◽  
Brain Regions ◽  
Evolution Model ◽  
Brain Morphology ◽  
Evolutionary Patterns ◽  
Mosaic Brain Evolution ◽  
The Brain ◽  
Regional Brain Volume

The brain plays a critical role in a wide variety of functions including behaviour, perception, motor control, and homeostatic maintenance. Each function can undergo different selective pressures over the course of evolution, and as selection acts on the outputs of brain function, it necessarily alters the structure of the brain. Two models have been proposed to explain the evolutionary patterns observed in brain morphology. The concerted brain evolution model posits that the brain evolves as a single unit and the evolution of different brain regions are coordinated. The mosaic brain evolution model posits that brain regions evolve independently of each other. It is now understood that both models are responsible for driving changes in brain morphology; however, which factors favour concerted or mosaic brain evolution is unclear. Here, we examined the volumes of the 6 major neural subdivisions across 14 species of the agamid lizard genus Ctenophorus (dragons). These species have diverged multiple times in behaviour, ecology, and body morphology, affording a unique opportunity to test neuroevolutionary models across species. We assigned each species to an ecomorph based on habitat use and refuge type, then used MRI to measure total and regional brain volume. We found evidence for both mosaic and concerted brain evolution in dragons: concerted brain evolution with respect to body size, and mosaic brain evolution with respect to ecomorph. Specifically, all brain subdivisions increase in volume relative to body size, yet the tectum and rhombencephalon also show opposite patterns of evolution with respect to ecomorph. Therefore, we find that both models of evolution are occurring simultaneously in the same structures in dragons, but are only detectable when examining particular drivers of selection. We show that the answer to the question of whether concerted or mosaic brain evolution is detected in a system can depend more on the type of selection measured than on the clade of animals studied.

scholarly journals Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

2015 ◽  
Vol 282 (1810) ◽  
pp. 20151008 ◽  
Author(s):  
Kristina Noreikiene ◽  
Gábor Herczeg ◽  
Abigél Gonda ◽  
Gergely Balázs ◽  
Arild Husby ◽  
...  
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Additive Genetic Variance ◽  
Genetic Correlations ◽  
Relative Size ◽  
Strong Support ◽  
Brain Evolution ◽  
Brain Regions ◽  
Independent Evolution ◽  
Mosaic Model

The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain, and its different regions in the three-spined stickleback ( Gasterosteus aculeatus ). We found that heritabilities were low (average h 2 = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average r G = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brain regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high ( r G = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks.

scholarly journals Rethinking the Effects of Body Size on the Study of Brain Size Evolution

2019 ◽  
Vol 93 (4) ◽  
pp. 182-195 ◽  
Author(s):  
Enrique Font ◽  
Roberto García-Roa ◽  
Daniel Pincheira-Donoso ◽  
Pau Carazo
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Scaling Effects ◽  
Selection Pressures ◽  
Body Tissues ◽  
Relative Brain Size ◽  
Functional Components ◽  
The Brain

Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.

IGF-1 in the Brain as a Regulator of Reproductive Neuroendocrine Function

2005 ◽  
Vol 230 (5) ◽  
pp. 292-306 ◽  
Author(s):  
Shabrine S. Daftary ◽  
Andrea C. Gore
Keyword(s):  
Critical Role ◽  
Somatic Growth ◽  
Reproductive Function ◽  
Brain Regions ◽  
Pituitary Hormones ◽  
Somatotropic Axis ◽  
Gnrh Neurons ◽  
Close Relationship ◽  
The Brain ◽  
Neuroendocrine Functions

Given the close relationship among neuroendocrine systems, it Is likely that there may be common signals that coordinate the acquisition of adult reproductive function with other homeo-static processes. In this review, we focus on central nervous system insulin-like growth factor-1 (IGF-1) as a signal controlling reproductive function, with possible links to somatic growth, particularly during puberty. In vertebrates, the appropriate neurosecretion of the decapeptide gonadotropin-releas-ing hormone (GnRH) plays a critical role in the progression of puberty. Gonadotropin-releasing hormone is released in pulses from neuroterminals in the median eminence (ME), and each GnRH pulse triggers the production of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These pituitary hormones in turn stimulate the synthesis and release of sex steroids by the gonads. Any factor that affects GnRH or gonadotropin pulsatility is important for puberty and reproductive function and, among these factors, the neurotrophic factor IGF-1 is a strong candidate. Although IGF-1 is most commonly studied as the tertiary peripheral hormone in the somatotropic axis via its synthesis in the liver, IGF-1 Is also synthesIzed in the brain, within neurons and glia. In neuroendocrine brain regions, central IGF-1 plays roles in the regulation of neuroendocrine functions, including direct actions on GnRH neurons. Moreover, GnRH neurons themselves co-express IGF-1 and the IGF-1 receptor, and this expression is developmentally regulated. Here, we examine the role of IGF-1 acting in the hypothalamus as a critical link between reproductive and other neuroendocrine functions.

scholarly journals Brain hubs defined in the group do not overlap with regions of high inter-individual variability

2021 ◽  
Author(s):  
Derek Martin Smith ◽  
Brian T Kraus ◽  
Ally Dworetsky ◽  
Evan M Gordon ◽  
Caterina Gratton
Keyword(s):  
Functional Connectivity ◽  
Brain Function ◽  
Critical Role ◽  
Brain Regions ◽  
Individual Variability ◽  
Spatial Proximity ◽  
Functional Magnetic Resonance ◽  
Multiple Networks ◽  
Human Connectome Project ◽  
The Brain

Connector 'hubs' are brain regions with links to multiple networks. These regions are hypothesized to play a critical role in brain function. While hubs are often identified based on group-average functional magnetic resonance imaging (fMRI) data, there is considerable inter-subject variation in the functional connectivity profiles of the brain, especially in association regions where hubs tend to be located. Here we investigated how group hubs are related to locations of inter-individual variability, to better understand if hubs are (a) relatively conserved across people, (b) locations with malleable connectivity, leading individuals to show variable hub profiles, or (c) artifacts arising from cross-person variation. To answer this question, we compared the locations of hubs and regions of strong idiosyncratic functional connectivity ("variants") in both the Midnight Scan Club and Human Connectome Project datasets. Group hubs defined based on the participation coefficient did not overlap strongly with variants. These hubs have relatively strong similarity across participants and consistent cross-network profiles. Consistency across participants was further improved when participation coefficient hubs were allowed to shift slightly in local position. Thus, our results demonstrate that group hubs defined with the participation coefficient are generally consistent across people, suggesting they may represent conserved cross-network bridges. More caution is warranted with alternative hub measures, such as community density, which are based on spatial proximity and show higher correspondence to locations of individual variability.

scholarly journals Rapid mosaic brain evolution under artificial selection for relative telencephalon size in the guppy (Poecilia reticulata)

2021 ◽  
Author(s):  
Stephanie Fong ◽  
Björn Rogell ◽  
Mirjam Amcoff ◽  
Alexander Kotrschal ◽  
Wouter van der Bijl ◽  
...  
Keyword(s):  
Artificial Selection ◽  
Poecilia Reticulata ◽  
Brain Size ◽  
Brain Evolution ◽  
Brain Regions ◽  
Research Field ◽  
Selected Lines ◽  
Vertebrate Brain ◽  
Offspring Production ◽  
Mosaic Brain Evolution

The vertebrate brain displays enormous morphological variation and the quest to understand the evolutionary causes and consequences of this variation has spurred much research. The mosaic brain evolution hypothesis, stating that brain regions can evolve relatively independently, is an important idea in this research field. Here we provide experimental support for this hypothesis through an artificial selection experiment in the guppy (Poecilia reticulata). After four generations of selection on relative telencephalon volume (relative to brain size) in replicated up-selected, down-selected and control-lines, we found substantial changes in telencephalon size, but no changes in other regions. Comparisons revealed that up-selected lines had larger telencephalon while down-selected lines had smaller telencephalon than wild Trinidadian populations. No cost of increasing telencephalon size was detected in offspring production. Our results support that independent evolutionary changes in specific brain regions through mosaic brain evolution can be important facilitators of cognitive evolution.

Task-fMRI Group and Functional Connectivity Analysis of the Brain During Faradarmani Consciousness Field Connection

2021 ◽  
Author(s):  
Mohammad Ali Taheri ◽  
Sara Torabi ◽  
Noushin Nabavi ◽  
Fatemeh Modarresi-Asem ◽  
Majid Abbasi Sisara ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Human Brain ◽  
Frontal Lobe ◽  
Critical Role ◽  
Group Analysis ◽  
Brain Regions ◽  
Connectivity Analysis ◽  
Functional Connectivity Analysis ◽  
Cognitive Activities ◽  
The Brain

Task fMRI has played a critical role in recognizing the specific functions of the different regions of human brain during various cognitive activities. This study aimed to investigate group analysis and functional connectivity in the Faradarmangars brain during the Faradarmani CF (FCF) connection. Using task functional MRI (task-fMRI), we attempted the identification of different activated and deactivated brain regions during the Consciousness Filed connection. Clusters that showed significant differences in peak intensity between task and rest group were selected as seeds for seed-voxel analysis. Connectivity of group differences in functional connectivity analysis was determined following each activation and deactivation network. In this study, we report the fMRI-based representation of the FCF connection at the human brain level. The group analysis of FCF connection task revealed activation of frontal lobe (BA6/BA10/BA11). Moreover, seed based functional connectivity analysis showed decreased connectivity within activated clusters and posterior Cingulate Gyrus (BA31). Moreover, we observed an increased connectivity within deactivated clusters and frontal lobe (BA11/BA47) during the FCF connection. Activation clusters as well as the increased and decreased connectivity between different regions of the brain during the FCF connection, firstly, validates the significant effect of the FCF and secondly, indicates a distinctive pattern of connection with this non-material and non-energetic field, in the brain.

scholarly journals Astroglial Isopotentiality and Calcium-Associated Biomagnetic Field Effects on Cortical Neuronal Coupling

Cells ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 439
Author(s):  
Marcos Martinez-Banaclocha
Keyword(s):  
Current Knowledge ◽  
Critical Role ◽  
Brain Regions ◽  
Local Magnetic Field ◽  
Field Potentials ◽  
Coherent Integration ◽  
Cognitive Faculties ◽  
Synaptic Neurotransmission ◽  
New Research ◽  
The Brain

Synaptic neurotransmission is necessary but does not sufficiently explain superior cognitive faculties. Growing evidence has shown that neuron–astroglial chemical crosstalk plays a critical role in the processing of information, computation, and memory. In addition to chemical and electrical communication among neurons and between neurons and astrocytes, other nonsynaptic mechanisms called ephaptic interactions can contribute to the neuronal synchronization from different brain regions involved in the processing of information. New research on brain astrocytes has clearly shown that the membrane potential of these cells remains very stable among neighboring and distant astrocytes due to the marked bioelectric coupling between them through gap junctions. This finding raises the possibility that the neocortical astroglial network exerts a guiding template modulating the excitability and synchronization of trillions of neurons by astroglial Ca2+-associated bioelectromagnetic interactions. We propose that bioelectric and biomagnetic fields of the astroglial network equalize extracellular local field potentials (LFPs) and associated local magnetic field potentials (LMFPs) in the cortical layers of the brain areas involved in the processing of information, contributing to the adequate and coherent integration of external and internal signals. This article reviews the current knowledge of ephaptic interactions in the cerebral cortex and proposes that the isopotentiality of cortical astrocytes is a prerequisite for the maintenance of the bioelectromagnetic crosstalk between neurons and astrocytes in the neocortex.

scholarly journals Immunohistochemical analysis of GFAP expression in the experimental sepsis-associated encephalopathy

Pathologia ◽  
2021 ◽  
Vol 18 (3) ◽  
pp. 295-302
Author(s):  
T. V. Shulyatnikova ◽  
V. O. Tumaskyi
Keyword(s):  
White Matter ◽  
Caudate Nucleus ◽  
Critical Role ◽  
Brain Regions ◽  
Subcortical White Matter ◽  
Control Group ◽  
Experimental Sepsis ◽  
Respiratory Impairment ◽  
Gfap Expression ◽  
The Brain

Pathophysiology of sepsis-associated encephalopathy (SAE) is linked to blood-brain barrier breakdown, neuroinflammation and neurotransmitter imbalance in the brain. Astroglia, the most abundant cell population within the brain, plays the critical role in control of all kinds of homeostatic processes, thereby regulating the adaptive reactions of the brain to various challenges. Astroglia are highly heterogenous across the brain regions, therefore, damaging factors stimulate heterogenous astroglial reactivity and response in different brain regions. The aim of this study was determining immunohistochemical features of GFAP expression in various brain regions in the model of rodent experimental sepsis. Materials and methods. The experiment was performed in Wistar rats: control group of 5 sham-operated rats and the main group of 20 rats subjected to cecum ligation and puncture (CLP) procedure. The immunohistochemical study of GFAP expression in the sensorimotor cortex, subcortical white matter, hippocampal, thalamic and caudate nucleus/putamen regions was performed from 20 to 48 hours of the postoperative period. Results. Starting from the 12th hour after CLP, animals began display progressive increase in signs of periorbital exudation, piloerection, fever-/hypothermia, diarrhea, social isolation, lethargy, and respiratory impairment. In the period of 20–38 hours, 9 animals showed expressed previously listed symptoms and were euthanized (CLP-B – lethal group), 11 rats survived until 48 hours of the experiment (CLP-A – survived group). In the lethal group, starting from 20 to 38 hours after the CLP procedure, a significant (relative to control) regionally-specific dynamic increase in the level of GFAP expression was observed in the brain: in the cortex – by 465 %, in the subcortical white matter – by 198 %, in the hippocampus – by 250 %, from the 23rd hour – in the caudate nucleus/putamen by 18 %. In the thalamus, no significant changes in the level of GFAP expression were observed. In the cortex and hippocampus of survived animals, 48 h after CLP, higher values of GFAP expression were observed comparing to the group of non-survived animals. Conclusions. Under conditions of the experimental SAE, an early dynamic increase in the astroglial reactivity was observed in the cortex, hippocampus, white matter, and caudate nucleus/putamen of the brain with the most significant increase of indicators in the cortex and hippocampus, which potentially indicates relatively more vulnerable areas of the brain to damaging factors, as well as places of the most active intercellular interaction in the condition of systemic inflammation. Higher values of GFAP expression in the cortex and hippocampus of survived animals at 48 hours of the experiment, compared with indicators of non-survived group, indicate increased astroglial reactivity in these brain regions at the noted time period, accompanied by relatively more favorable clinical course of the disease.  

The relationships between brain regions and forelimb dexterity in marsupials (Marsupialia): a comparative test of the principle of proper mass

2000 ◽  
Vol 48 (1) ◽  
pp. 99 ◽  
Author(s):  
Andrew N. Iwaniuk ◽  
John E. Nelson ◽  
Ian Q. Whishaw
Keyword(s):  
Brain Cortex ◽  
Brain Size ◽  
Brain Regions ◽  
Brain Morphology ◽  
Proper Mass ◽  
Contrast Analysis ◽  
Independent Contrast ◽  
The Relationship ◽  
The Brain ◽  
Forelimb Movements

A behavioural index of forelimb dexterity and comparative statistics were used to analyse the relationships between proximal (shoulder, upper and lower forelimb) and distal (wrist, forepaw, digits) forelimb dexterity and four aspects of brain morphology (overall brain, cortex, cerebellum and telencephalon sizes) in 18 species of marsupials. On the basis of the principle of proper mass, it was expected that an increase in forelimb dexterity (either proximal or distal) would be positively correlated with the size of the brain and the three brain components. Using independent contrast analysis to remove the effects of phylogeny revealed three significant correlations between: cortex size and distal dexterity, cerebellum size and proximal dexterity, and telencephalon size and distal dexterity. The relationship between cortex size and distal dexterity was subsequently corroborated by Spearman rank correlations. These results suggest that the execution of finely coordinated forelimb movements may not be dependent upon overall brain size, but may be dependent upon the size of brain components, thus supporting the principle of proper mass.

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