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Magrou L, Joyce MKP, Froudist-Walsh S, Datta D, Wang XJ, Martinez-Trujillo J, Arnsten AFT. The meso-connectomes of mouse, marmoset, and macaque: network organization and the emergence of higher cognition. Cereb Cortex 2024; 34:bhae174. [PMID: 38771244 PMCID: PMC11107384 DOI: 10.1093/cercor/bhae174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/29/2024] [Accepted: 04/08/2024] [Indexed: 05/22/2024] Open
Abstract
The recent publications of the inter-areal connectomes for mouse, marmoset, and macaque cortex have allowed deeper comparisons across rodent vs. primate cortical organization. In general, these show that the mouse has very widespread, "all-to-all" inter-areal connectivity (i.e. a "highly dense" connectome in a graph theoretical framework), while primates have a more modular organization. In this review, we highlight the relevance of these differences to function, including the example of primary visual cortex (V1) which, in the mouse, is interconnected with all other areas, therefore including other primary sensory and frontal areas. We argue that this dense inter-areal connectivity benefits multimodal associations, at the cost of reduced functional segregation. Conversely, primates have expanded cortices with a modular connectivity structure, where V1 is almost exclusively interconnected with other visual cortices, themselves organized in relatively segregated streams, and hierarchically higher cortical areas such as prefrontal cortex provide top-down regulation for specifying precise information for working memory storage and manipulation. Increased complexity in cytoarchitecture, connectivity, dendritic spine density, and receptor expression additionally reveal a sharper hierarchical organization in primate cortex. Together, we argue that these primate specializations permit separable deconstruction and selective reconstruction of representations, which is essential to higher cognition.
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Affiliation(s)
- Loïc Magrou
- Department of Neural Science, New York University, New York, NY 10003, United States
| | - Mary Kate P Joyce
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, United States
| | - Sean Froudist-Walsh
- School of Engineering Mathematics and Technology, University of Bristol, Bristol, BS8 1QU, United Kingdom
| | - Dibyadeep Datta
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06510, United States
| | - Xiao-Jing Wang
- Department of Neural Science, New York University, New York, NY 10003, United States
| | - Julio Martinez-Trujillo
- Departments of Physiology and Pharmacology, and Psychiatry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 3K7, Canada
| | - Amy F T Arnsten
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, United States
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2
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Garcia-Marin V, Kelly JG, Hawken MJ. Neuronal composition of processing modules in human V1: laminar density for neuronal and non-neuronal populations and a comparison with macaque. Cereb Cortex 2024; 34:bhad512. [PMID: 38183210 PMCID: PMC10839852 DOI: 10.1093/cercor/bhad512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 12/07/2023] [Accepted: 12/08/2023] [Indexed: 01/07/2024] Open
Abstract
The neuronal composition of homologous brain regions in different primates is important for understanding their processing capacities. Primary visual cortex (V1) has been widely studied in different members of the catarrhines. Neuronal density is considered to be central in defining the structure-function relationship. In human, there are large variations in the reported neuronal density from prior studies. We found the neuronal density in human V1 was 79,000 neurons/mm3, which is 35% of the neuronal density previously determined in macaque V1. Laminar density was proportionally similar between human and macaque. In V1, the ocular dominance column (ODC) contains the circuits for the emergence of orientation preference and spatial processing of a point image in many mammalian species. Analysis of the total neurons in an ODC and of the full number of neurons in macular vision (the central 15°) indicates that humans have 1.3× more neurons than macaques even though the density of neurons in macaque is 3× the density in human V1. We propose that the number of neurons in a functional processing unit rather than the number of neurons under a mm2 of cortex is more appropriate for cortical comparisons across species.
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Affiliation(s)
| | - Jenna G Kelly
- Center for Neural Science, New York University, New York City, NY 10003, United States
| | - Michael J Hawken
- Center for Neural Science, New York University, New York City, NY 10003, United States
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3
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Mortberg MA, Gentile JE, Nadaf N, Vanderburg C, Simmons S, Dubinsky D, Slamin A, Maldonado S, Petersen C, Jones N, Kordasiewicz H, Zhao H, Vallabh S, Minikel E. A single-cell map of antisense oligonucleotide activity in the brain. Nucleic Acids Res 2023; 51:7109-7124. [PMID: 37188501 PMCID: PMC10415122 DOI: 10.1093/nar/gkad371] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/19/2023] [Accepted: 04/27/2023] [Indexed: 05/17/2023] Open
Abstract
Antisense oligonucleotides (ASOs) dosed into cerebrospinal fluid (CSF) distribute broadly throughout the central nervous system (CNS). By modulating RNA, they hold the promise of targeting root molecular causes of disease and hold potential to treat myriad CNS disorders. Realization of this potential requires that ASOs must be active in the disease-relevant cells, and ideally, that monitorable biomarkers also reflect ASO activity in these cells. The biodistribution and activity of such centrally delivered ASOs have been deeply characterized in rodent and non-human primate (NHP) models, but usually only in bulk tissue, limiting our understanding of the distribution of ASO activity across individual cells and across diverse CNS cell types. Moreover, in human clinical trials, target engagement is usually monitorable only in a single compartment, CSF. We sought a deeper understanding of how individual cells and cell types contribute to bulk tissue signal in the CNS, and how these are linked to CSF biomarker outcomes. We employed single nucleus transcriptomics on tissue from mice treated with RNase H1 ASOs against Prnp and Malat1 and NHPs treated with an ASO against PRNP. Pharmacologic activity was observed in every cell type, though sometimes with substantial differences in magnitude. Single cell RNA count distributions implied target RNA suppression in every single sequenced cell, rather than intense knockdown in only some cells. Duration of action up to 12 weeks post-dose differed across cell types, being shorter in microglia than in neurons. Suppression in neurons was generally similar to, or more robust than, the bulk tissue. In macaques, PrP in CSF was lowered 40% in conjunction with PRNP knockdown across all cell types including neurons, arguing that a CSF biomarker readout is likely to reflect ASO pharmacodynamic effect in disease-relevant cells in a neuronal disorder. Our results provide a reference dataset for ASO activity distribution in the CNS and establish single nucleus sequencing as a method for evaluating cell type specificity of oligonucleotide therapeutics and other modalities.
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Affiliation(s)
- Meredith A Mortberg
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Juliana E Gentile
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Naeem M Nadaf
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Charles Vanderburg
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Sean Simmons
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Dan Dubinsky
- Genomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Adam Slamin
- Genomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Salome Maldonado
- Genomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Caroline L Petersen
- Genomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Nichole Jones
- Genomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | | | - Hien T Zhao
- Ionis Pharmaceuticals, Carlsbad, CA 92010, USA
| | - Sonia M Vallabh
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- McCance Center for Brain Health and Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA02115, USA
- Prion Alliance, Cambridge, MA 02139, USA
| | - Eric Vallabh Minikel
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- McCance Center for Brain Health and Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA02115, USA
- Prion Alliance, Cambridge, MA 02139, USA
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4
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Cunha F, Gutiérrez-Ibáñez C, Brinkman B, Wylie DR, Iwaniuk AN. The relative sizes of nuclei in the oculomotor complex vary by order and behaviour in birds. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 209:341-360. [PMID: 36522507 DOI: 10.1007/s00359-022-01598-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 10/26/2022] [Accepted: 11/25/2022] [Indexed: 12/23/2022]
Abstract
Eye movements are a critical component of visually guided behaviours, allowing organisms to scan the environment and bring stimuli of interest to regions of acuity in the retina. Although the control and modulation of eye movements by cranial nerve nuclei are highly conserved across vertebrates, species variation in visually guided behaviour and eye morphology could lead to variation in the size of oculomotor nuclei. Here, we test for differences in the size and neuron numbers of the oculomotor nuclei among birds that vary in behaviour and eye morphology. Using unbiased stereology, we measured the volumes and numbers of neurons of the oculomotor (nIII), trochlear (nIV), abducens (nVI), and Edinger-Westphal (EW) nuclei across 71 bird species and analysed these with phylogeny-informed statistics. Owls had relatively smaller nIII, nIV, nVI and EW nuclei than other birds, which reflects their limited degrees of eye movements. In contrast, nVI was relatively larger in falcons and hawks, likely reflecting how these predatory species must shift focus between the central and temporal foveae during foraging and prey capture. Unexpectedly, songbirds had an enlarged EW and relatively more nVI neurons, which might reflect accommodation and horizontal eye movements. Finally, the one merganser we measured also has an enlarged EW, which is associated with the high accommodative power needed for pursuit diving. Overall, these differences reflect species and clade level variation in behaviour, but more data are needed on eye movements in birds across species to better understand the relationships among behaviour, retinal anatomy, and brain anatomy.
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Affiliation(s)
- Felipe Cunha
- Department of Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4, Canada
| | | | - Benjamin Brinkman
- Department of Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4, Canada
| | - Douglas R Wylie
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Andrew N Iwaniuk
- Department of Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4, Canada.
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5
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Cunha F, Stingo-Hirmas D, Cardoso RF, Wright D, Henriksen R. Neuronal and non-neuronal scaling across brain regions within an intercross of domestic and wild chickens. Front Neuroanat 2022; 16:1048261. [PMID: 36506870 PMCID: PMC9732670 DOI: 10.3389/fnana.2022.1048261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 11/11/2022] [Indexed: 11/26/2022] Open
Abstract
The allometric scaling of the brain size and neuron number across species has been extensively studied in recent years. With the exception of primates, parrots, and songbirds, larger brains have more neurons but relatively lower neuronal densities than smaller brains. Conversely, when considering within-population variability, it has been shown that mice with larger brains do not necessarily have more neurons but rather more neurons in the brain reflect higher neuronal density. To what extent this intraspecific allometric scaling pattern of the brain applies to individuals from other species remains to be explored. Here, we investigate the allometric relationships among the sizes of the body, brain, telencephalon, cerebellum, and optic tectum, and the numbers of neurons and non-neuronal cells of the telencephalon, cerebellum, and optic tectum across 66 individuals originated from an intercross between wild and domestic chickens. Our intercross of chickens generates a population with high variation in brain size, making it an excellent model to determine the allometric scaling of the brain within population. Our results show that larger chickens have larger brains with moderately more neurons and non-neuronal cells. Yet, absolute number of neurons and non-neuronal cells correlated strongly and positively with the density of neurons and non-neuronal cells, respectively. As previously shown in mice, this scaling pattern is in stark contrast with what has been found across different species. Our findings suggest that neuronal scaling rules across species are not a simple extension of the neuronal scaling rules that apply within a species, with important implications for the evolutionary developmental origins of brain diversity.
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6
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Himmelberg MM, Winawer J, Carrasco M. Linking individual differences in human primary visual cortex to contrast sensitivity around the visual field. Nat Commun 2022; 13:3309. [PMID: 35697680 PMCID: PMC9192713 DOI: 10.1038/s41467-022-31041-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 05/06/2022] [Indexed: 11/09/2022] Open
Abstract
A central question in neuroscience is how the organization of cortical maps relates to perception, for which human primary visual cortex (V1) is an ideal model system. V1 nonuniformly samples the retinal image, with greater cortical magnification (surface area per degree of visual field) at the fovea than periphery and at the horizontal than vertical meridian. Moreover, the size and cortical magnification of V1 varies greatly across individuals. Here, we used fMRI and psychophysics in the same observers to quantify individual differences in V1 cortical magnification and contrast sensitivity at the four polar angle meridians. Across observers, the overall size of V1 and localized cortical magnification positively correlated with contrast sensitivity. Moreover, greater cortical magnification and higher contrast sensitivity at the horizontal than the vertical meridian were strongly correlated. These data reveal a link between cortical anatomy and visual perception at the level of individual observer and stimulus location.
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Affiliation(s)
- Marc M Himmelberg
- Department of Psychology, New York University, New York, NY, 10003, USA.
- Center for Neural Science, New York University, New York, NY, 10003, USA.
| | - Jonathan Winawer
- Department of Psychology, New York University, New York, NY, 10003, USA
- Center for Neural Science, New York University, New York, NY, 10003, USA
| | - Marisa Carrasco
- Department of Psychology, New York University, New York, NY, 10003, USA
- Center for Neural Science, New York University, New York, NY, 10003, USA
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7
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McNeil RM, Devigili A, Kolm N, Fitzpatrick JL. Does brain size affect mate choice? An experimental examination in pygmy halfbeaks. Behav Ecol 2021; 32:1103-1113. [PMID: 34949959 PMCID: PMC8691582 DOI: 10.1093/beheco/arab046] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 03/26/2021] [Accepted: 04/22/2021] [Indexed: 11/16/2022] Open
Abstract
Choosing a mate is one of the most important decisions in an animal's lifetime. Female mate choice is often guided by the presence or intensity of male sexual ornaments, which must be integrated and compared among potential mates. Individuals with greater cognitive abilities may be better at evaluating and comparing sexual ornaments, even when the difference in ornaments is small. While brain size is often used as a proxy for cognitive ability, its effect on mate choice has rarely been investigated. Here, we investigate the effect of brain size on mate preferences in the pygmy halfbeak Dermogenys collettei, a small freshwater fish that forms mixed-sex shoals where mating takes place. Pygmy halfbeaks are ideal models as their semi-transparent heads allow for external brain measurements. After validating the use of external measurements as a proxy for internal brain size, we presented females with large or small brains (relative to body length) with two males that had either a large or small difference in sexual ornamentation (measured by the total area of red coloration). Unexpectedly, neither total relative brain size nor relative telencephalon size affected any measured aspect of mate preference. However, the difference in male sexual ornamentation did affect preference, with females preferring males with a smaller area of red coloration when the difference in ornaments was large. This study highlights the complexities of mate choice and the importance of considering a range of stimuli when examining mate preferences.
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Affiliation(s)
- Rebecca M McNeil
- Department of Zoology: Ethology, Stockholm University, Svante Arrhenius väg 18b, 106 91 Stockholm, Sweden
| | - Alessandro Devigili
- Department of Zoology: Ethology, Stockholm University, Svante Arrhenius väg 18b, 106 91 Stockholm, Sweden
| | - Niclas Kolm
- Department of Zoology: Ethology, Stockholm University, Svante Arrhenius väg 18b, 106 91 Stockholm, Sweden
| | - John L Fitzpatrick
- Department of Zoology: Ethology, Stockholm University, Svante Arrhenius väg 18b, 106 91 Stockholm, Sweden
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8
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Makarova AA, Polilov AA, Chklovskii DB. Small brains for big science. Curr Opin Neurobiol 2021; 71:77-83. [PMID: 34656052 DOI: 10.1016/j.conb.2021.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 08/30/2021] [Accepted: 09/06/2021] [Indexed: 01/03/2023]
Abstract
As the study of the human brain is complicated by its sheer scale, complexity, and impracticality of invasive experiments, neuroscience research has long relied on model organisms. The brains of macaque, mouse, zebrafish, fruit fly, nematode, and others have yielded many secrets that advanced our understanding of the human brain. Here, we propose that adding miniature insects to this collection would reduce the costs and accelerate brain research. The smallest insects occupy a special place among miniature animals: despite their body sizes, comparable to unicellular organisms, they retain complex brains that include thousands of neurons. Their brains possess the advantages of those in insects, such as neuronal identifiability and the connectome stereotypy, yet are smaller and hence easier to map and understand. Finally, the brains of miniature insects offer insights into the evolution of brain design.
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Affiliation(s)
| | - Alexey A Polilov
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Dmitri B Chklovskii
- CCN, Flatiron Institute and Neuroscience Institute, NYUMC, New York, United States.
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9
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Cunha F, Gutiérrez-Ibáñez C, Racicot K, Wylie DR, Iwaniuk AN. A quantitative analysis of cerebellar anatomy in birds. Brain Struct Funct 2021; 226:2561-2583. [PMID: 34357439 DOI: 10.1007/s00429-021-02352-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 07/26/2021] [Indexed: 12/19/2022]
Abstract
The cerebellum is largely conserved in its circuitry, but varies greatly in size and shape across species. The extent to which differences in cerebellar morphology is driven by changes in neuron numbers, neuron sizes or both, remains largely unknown. To determine how species variation in cerebellum size and shape is reflective of neuron sizes and numbers requires the development of a suitable comparative data set and one that can effectively separate different neuronal populations. Here, we generated the largest comparative dataset to date on neuron numbers, sizes, and volumes of cortical layers and surface area of the cerebellum across 54 bird species. Across different cerebellar sizes, the cortical layers maintained relatively constant proportions to one another and variation in cerebellum size was largely due to neuron numbers rather than neuron sizes. However, the rate at which neuron numbers increased with cerebellum size varied across Purkinje cells, granule cells, and cerebellar nuclei neurons. We also examined the relationship among neuron numbers, cerebellar surface area and cerebellar folding. Our estimate of cerebellar folding, the midsagittal foliation index, was a poor predictor of surface area and number of Purkinje cells, but surface area was the best predictor of Purkinje cell numbers. Overall, this represents the first comprehensive, quantitative analysis of cerebellar anatomy in a comparative context of any vertebrate. The extent to which these relationships occur in other vertebrates requires a similar approach and would determine whether the same scaling principles apply throughout the evolution of the cerebellum.
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Affiliation(s)
- Felipe Cunha
- Department of Neuroscience, University of Lethbridge, 4401 University Dr. W, Science & Academic Building, SA8150, Lethbridge, AB, T1K 6T5, Canada.
| | | | - Kelsey Racicot
- Department of Neuroscience, University of Lethbridge, 4401 University Dr. W, Science & Academic Building, SA8150, Lethbridge, AB, T1K 6T5, Canada
| | - Douglas R Wylie
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Andrew N Iwaniuk
- Department of Neuroscience, University of Lethbridge, 4401 University Dr. W, Science & Academic Building, SA8150, Lethbridge, AB, T1K 6T5, Canada
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10
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Bartkowska K, Turlejski K, Tepper B, Rychlik L, Vogel P, Djavadian R. Effects of Brain Size on Adult Neurogenesis in Shrews. Int J Mol Sci 2021; 22:7664. [PMID: 34299282 PMCID: PMC8303847 DOI: 10.3390/ijms22147664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/14/2021] [Accepted: 07/14/2021] [Indexed: 01/02/2023] Open
Abstract
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.
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Affiliation(s)
- Katarzyna Bartkowska
- Nencki Institute of Experimental Biology Polish Academy of Sciences, 02-093 Warsaw, Poland; (K.B.); (B.T.)
| | - Krzysztof Turlejski
- Faculty of Biology and Environmental Sciences, Cardinal Stefan Wyszynski University in Warsaw, 01-938 Warsaw, Poland;
| | - Beata Tepper
- Nencki Institute of Experimental Biology Polish Academy of Sciences, 02-093 Warsaw, Poland; (K.B.); (B.T.)
| | - Leszek Rychlik
- Department of Systematic Zoology, Institute of Environmental Biology, Adam Mickiewicz University, 61-712 Poznan, Poland;
| | - Peter Vogel
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland;
| | - Ruzanna Djavadian
- Nencki Institute of Experimental Biology Polish Academy of Sciences, 02-093 Warsaw, Poland; (K.B.); (B.T.)
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11
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A Review of Effects of Environment on Brain Size in Insects. INSECTS 2021; 12:insects12050461. [PMID: 34067515 PMCID: PMC8156428 DOI: 10.3390/insects12050461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/03/2021] [Accepted: 05/12/2021] [Indexed: 11/16/2022]
Abstract
Simple Summary What makes a big brain is fascinating since it is considered as a measure of intelligence. Above all, brain size is associated with body size. If species that have evolved with complex social behaviours possess relatively bigger brains than those deprived of such behaviours, this does not constitute the only factor affecting brain size. Other factors such as individual experience or surrounding environment also play roles in the size of the brain. In this review, I summarize the recent findings about the effects of environment on brain size in insects. I also discuss evidence about how the environment has an impact on sensory systems and influences brain size. Abstract Brain size fascinates society as well as researchers since it is a measure often associated with intelligence and was used to define species with high “intellectual capabilities”. In general, brain size is correlated with body size. However, there are disparities in terms of relative brain size between species that may be explained by several factors such as the complexity of social behaviour, the ‘social brain hypothesis’, or learning and memory capabilities. These disparities are used to classify species according to an ‘encephalization quotient’. However, environment also has an important role on the development and evolution of brain size. In this review, I summarise the recent studies looking at the effects of environment on brain size in insects, and introduce the idea that the role of environment might be mediated through the relationship between olfaction and vision. I also discussed this idea with studies that contradict this way of thinking.
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12
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Kverková K, Polonyiová A, Kubička L, Němec P. Individual and age-related variation of cellular brain composition in a squamate reptile. Biol Lett 2020; 16:20200280. [PMID: 32961085 DOI: 10.1098/rsbl.2020.0280] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Within-species variation in the number of neurons, other brain cells and their allocation to different brain parts is poorly studied. Here, we assess these numbers in a squamate reptile, the Madagascar ground gecko (Paroedura picta). We examined adults from two captive populations and three age groups within one population. Even though reptiles exhibit extensive adult neurogenesis, intrapopulation variation in the number of neurons is similar to that in mice. However, the two populations differed significantly in most measures, highlighting the fact that using only one population can underestimate within-species variation. There is a substantial increase in the number of neurons and decrease in neuronal density in adult geckos relative to hatchlings and an increase in the number of neurons in the telencephalon in fully grown adults relative to sexually mature young adults. This finding implies that adult neurogenesis does not only replace worn out but also adds new telencephalic neurons in reptiles during adulthood. This markedly contrasts with the situation in mammals, where the number of cortical neurons declines with age.
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Affiliation(s)
- Kristina Kverková
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, CZ-128 44 Praha 2, Czech Republic
| | - Alexandra Polonyiová
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, CZ-128 44 Praha 2, Czech Republic
| | - Lukáš Kubička
- Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-128 44 Praha 2, Czech Republic
| | - Pavel Němec
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, CZ-128 44 Praha 2, Czech Republic
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13
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Neves K, Guercio GD, Anjos-Travassos Y, Costa S, Perozzo A, Montezuma K, Herculano-Houzel S, Panizzutti R. The relationship between the number of neurons and behavioral performance in Swiss mice. Neurosci Lett 2020; 735:135202. [PMID: 32599318 DOI: 10.1016/j.neulet.2020.135202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 06/21/2020] [Indexed: 10/24/2022]
Abstract
Neuronal number varies by several orders of magnitude across species, and has been proposed to predict cognitive capability across species. Remarkably, numbers of neurons vary across individual mice by a factor of 2 or more. We directly addressed the question of whether there is a relationship between performance in behavioral tests and the number of neurons in functionally relevant structures in the mouse brain. Naïve Swiss mice went through a battery of behavioral tasks designed to measure cognitive, motor and olfactory skills. We estimated the number of neurons in different brain regions (cerebral cortex, hippocampus, olfactory bulb, cerebellum and remaining areas) and crossed the two datasets to test the a priori hypothesis of correlation between cognitive abilities and numbers of neurons. Surprisingly, performance in the behavioral tasks did not correlate strongly with number of neurons in any of the brain regions studied. Our results show that whereas neuronal number is a predictor of cognitive skills across species, it is not a good predictor of cognitive, sensory or motor ability across individuals within a species, which suggests that other factors are more relevant for explaining cognitive differences between individuals of the same species.
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Affiliation(s)
- Kleber Neves
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Brazil; Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil.
| | - Gerson Duarte Guercio
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil; Department of Psychiatry, University of Minnesota, 2312 S 6th St., Minneapolis, MN, United States.
| | - Yuri Anjos-Travassos
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil
| | - Stella Costa
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil
| | - Ananda Perozzo
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil
| | - Karine Montezuma
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil
| | - Suzana Herculano-Houzel
- Department of Psychology, Department of Biological Sciences, Vanderbilt Brain Institute, Vanderbilt University, United States
| | - Rogério Panizzutti
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil; Instituto de Psiquiatria, Universidade Federal do Rio de Janeiro, Brazil
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14
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El-Andari R, Cunha F, Tschirren B, Iwaniuk AN. Selection for Divergent Reproductive Investment Affects Neuron Size and Foliation in the Cerebellum. BRAIN, BEHAVIOR AND EVOLUTION 2020; 95:69-77. [PMID: 32784306 DOI: 10.1159/000509068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 06/02/2020] [Indexed: 11/19/2022]
Abstract
The cerebellum has a highly conserved internal circuitry, but varies greatly in size and morphology within and across species. Despite this variation, the underlying volumetric changes among the layers of the cerebellar cortex or their association with Purkinje cell numbers and sizes is poorly understood. Here, we examine intraspecific scaling relationships and variation in the quantitative neuroanatomy of the cerebellum in Japanese quail (Coturnix japonica) selected for high or low reproductive investment. As predicted by the circuitry of the cerebellum, the volumes of the constituent layers of the cerebellar cortex were strongly and positively correlated with one another and with total cerebellar volume. The number of Purkinje cells also significantly and positively co-varied with total cerebellar volume and the molecular layer, but not the granule cell layer or white matter volumes. Purkinje cell size and cerebellar foliation did not significantly covary with any cerebellar measures, but differed significantly between the selection lines. Males and females from the high-investment lines had smaller Purkinje cells than males and females from the low-investment lines and males from the high-investment lines had less folded cerebella than quail from the low-investment lines. These results suggest that within species, the layers of the cerebellum increase in a coordinated fashion, but Purkinje cell size and cerebellar foliation do not increase proportionally with overall cerebellum size. In contrast, selection for differential reproductive investment affects Purkinje cell size and cerebellar foliation, but not other quantitative measures of cerebellar anatomy.
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Affiliation(s)
- Ryaan El-Andari
- Department of Neuroscience, University of Lethbridge, Lethbridge, Alberta, Canada
| | - Felipe Cunha
- Department of Neuroscience, University of Lethbridge, Lethbridge, Alberta, Canada
| | - Barbara Tschirren
- Centre for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | - Andrew N Iwaniuk
- Department of Neuroscience, University of Lethbridge, Lethbridge, Alberta, Canada,
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15
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Cunha F, Racicot K, Nahirney J, Heuston C, Wylie D, Iwaniuk A. Allometric Scaling Rules of the Cerebellum in Galliform Birds. BRAIN, BEHAVIOR AND EVOLUTION 2020; 95:78-92. [DOI: 10.1159/000509069] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 06/02/2020] [Indexed: 11/19/2022]
Abstract
Although the internal circuitry of the cerebellum is highly conserved across vertebrate species, the size and shape of the cerebellum varies considerably. Recent comparative studies have examined the allometric rules between cerebellar mass and number of neurons, but data are lacking on the numbers and sizes of Purkinje and granule cells or scaling of cerebellar foliation. Here, we investigate the allometric rules that govern variation in the volumes of the layers of the cerebellum, the numbers and sizes of Purkinje cells and granule cells and the degree of the cerebellar foliation across 7 species of galliform birds. We selected Galliformes because they vary greatly in body and brain sizes. Our results show that the molecular, granule and white matter layers all increase in volume at the same rate relative to total cerebellum volume. Both numbers and sizes of Purkinje cells increased with cerebellar volume, but numbers of Purkinje cells increased at a much faster rate than size. Granule cell numbers increased with cerebellar volume, but size did not. Sizes and numbers of Purkinje cells as well as numbers of granule cells were positively correlated with the degree of cerebellar foliation, but granule cell size decreased with higher degrees of foliation. The concerted changes among the volumes of cerebellar layers likely reflects the conserved neural circuitry of the cerebellum. Also, our data indicate that the scaling of cell sizes can vary markedly across neuronal populations, suggesting that evolutionary changes in cell sizes might be more complex than what is often assumed.
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16
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Similar Microglial Cell Densities across Brain Structures and Mammalian Species: Implications for Brain Tissue Function. J Neurosci 2020; 40:4622-4643. [PMID: 32253358 DOI: 10.1523/jneurosci.2339-19.2020] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 12/10/2019] [Accepted: 01/05/2020] [Indexed: 12/30/2022] Open
Abstract
Microglial cells play essential volume-related actions in the brain that contribute to the maturation and plasticity of neural circuits that ultimately shape behavior. Microglia can thus be expected to have similar cell sizes and even distribution both across brain structures and across species with different brain sizes. To test this hypothesis, we determined microglial cell densities (the inverse of cell size) using immunocytochemistry to Iba1 in samples of free cell nuclei prepared with the isotropic fractionator from brain structures of 33 mammalian species belonging to males and females of five different clades. We found that microglial cells constitute ∼7% of non-neuronal cells in different brain structures as well as in the whole brain of all mammalian species examined. Further, they vary little in cell density compared with neuronal cell densities within the cerebral cortex, across brain structures, across species within the same clade, and across mammalian clades. As a consequence, we find that one microglial cell services as few as one and as many as 100 neurons in different brain regions and species, depending on the local neuronal density. We thus conclude that the addition of microglial cells to mammalian brains is governed by mechanisms that constrain the size of these cells and have remained conserved over 200 million years of mammalian evolution. We discuss the probable consequences of such constrained size for brain function in health and disease.SIGNIFICANCE STATEMENT Microglial cells are resident macrophages of the CNS, with key functions in recycling synapses and maintaining the local environment in health and disease. We find that microglial cells occur in similar densities in the brains of different species and in the different structures of each individual brain, which indicates that these cells maintain a similar average size in mammalian evolution, suggesting in turn that the volume monitored by each microglial cell remains constant across mammals. Because the density of neurons is highly variable across the same brain structures and species, our finding implies that microglia-dependent functional recovery may be particularly difficult in those brain structures and species with high neuronal densities and therefore fewer microglial cells per neuron.
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17
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Němec P, Osten P. The evolution of brain structure captured in stereotyped cell count and cell type distributions. Curr Opin Neurobiol 2020; 60:176-183. [PMID: 31945723 PMCID: PMC7191610 DOI: 10.1016/j.conb.2019.12.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 12/13/2022]
Abstract
The stereotyped features of brain structure, such as the distribution, morphology and connectivity of neuronal cell types across brain areas, are those most likely to explain the remarkable capacity of the brain to process information and govern behaviors. Recent advances in anatomical methods, including the simple but versatile isotropic fractionator and several whole-brain labeling, clearing and microscopy methods, have opened the door to an exciting new era in comparative brain anatomy, one that has the potential to transform our understanding of the brain structure-function relationship by representing the evolution of brain complexity in quantitative anatomical features shared across species and species-specific or clade-specific. Here we discuss these methods and their application to mapping brain cell count and cell type distributions-two particularly powerful neural correlates of vertebrate cognitive and behavioral capabilities.
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Affiliation(s)
- Pavel Němec
- Department of Zoology, Faculty of Science, Charles University, Vinicna 7, 12844 Prague, Czech Republic.
| | - Pavel Osten
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11743, USA.
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18
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Pendergraft LT, Lehnert AL, Marzluff JM. Individual and social factors affecting the ability of American crows to solve and master a string pulling task. Ethology 2020; 126:229-245. [PMID: 33776175 PMCID: PMC7996111 DOI: 10.1111/eth.12980] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 10/17/2019] [Indexed: 12/16/2022]
Abstract
Crows and other birds in the family Corvidae regularly share information to learn the identity and whereabouts of dangerous predators, but can they use social learning to solve a novel task for a food reward? Here we examined the factors affecting the ability of 27 wild-caught American crows to solve a common string-pulling task in a laboratory setting. We split crows into two groups; one group was given the task after repeatedly observing a conspecific model the solution, the other solved in the absence of conspecific models. We recorded the crows' estimated age, sex, size, body condition, level of nervousness, and brain volume using DICOM images from a CT scan. Although none of these variables were statistically significant, crows without a conspecific model and large brain volumes consistently mastered the task in the minimum number of days, whereas those with conspecific models and smaller brain volumes required varying and sometimes a substantial number of days to master the task. We found indirect evidence that body condition might also be important for motivating crows to solve the task. Crows with conspecific models were no more likely to initially solve the task than those working the puzzle without social information, but those that mastered the task usually copied the method most frequently demonstrated by their knowledgeable neighbors. These findings suggest that brain volume and possibly body condition may be factors in learning new tasks, and that crows can use social learning to refine their ability to obtain a novel food source, although they must initially learn to access it themselves.
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Affiliation(s)
| | | | - John M. Marzluff
- University of Washington, School of Environmental and Forest Sciences
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19
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Marhounová L, Kotrschal A, Kverková K, Kolm N, Němec P. Artificial selection on brain size leads to matching changes in overall number of neurons. Evolution 2019; 73:2003-2012. [PMID: 31339177 PMCID: PMC6772110 DOI: 10.1111/evo.13805] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 06/13/2019] [Accepted: 06/19/2019] [Indexed: 12/16/2022]
Abstract
Neurons are the basic computational units of the brain, but brain size is the predominant surrogate measure of brain functional capacity in comparative and cognitive neuroscience. This approach is based on the assumption that larger brains harbor higher numbers of neurons and their connections, and therefore have a higher information-processing capacity. However, recent studies have shown that brain mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine the relationship between evolutionary changes in brain size and the number of brain neurons. Here, we provide such a test by comparing neuron number in artificial selection lines of female guppies (Poecilia reticulata) with >15% difference in relative brain mass and numerous previously demonstrated cognitive differences. Using the isotropic fractionator, we demonstrate that large-brained females have a higher overall number of neurons than small-brained females, but similar neuronal densities. Importantly, this difference holds also for the telencephalon, a key region for cognition. Our study provides the first direct experimental evidence that selection for brain mass leads to matching changes in number of neurons and shows that brain size evolution is intimately linked to the evolution of neuron number and cognition.
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Affiliation(s)
- Lucie Marhounová
- Department of Zoology, Faculty of ScienceCharles University12844PragueCzech Republic
| | - Alexander Kotrschal
- Behavioural Ecology GroupDepartment of Animal Sciences6708wdWageningenNetherlands
- Department of Zoology/EthologyStockholm University10691StockholmSweden
| | - Kristina Kverková
- Department of Zoology, Faculty of ScienceCharles University12844PragueCzech Republic
| | - Niclas Kolm
- Department of Zoology/EthologyStockholm University10691StockholmSweden
| | - Pavel Němec
- Department of Zoology, Faculty of ScienceCharles University12844PragueCzech Republic
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20
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The reliability of the isotropic fractionator method for counting total cells and neurons. J Neurosci Methods 2019; 326:108392. [PMID: 31394117 DOI: 10.1016/j.jneumeth.2019.108392] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 07/21/2019] [Accepted: 08/03/2019] [Indexed: 11/21/2022]
Abstract
BACKGROUND The Isotropic Fractionator (IF) is a method to determine the cellular composition of nervous tissue. It has been mostly applied to assess variation across species, where differences are expected to be large enough not to be masked by methodological error. However, understanding the sources of variation in the method is important if the goal is to detect smaller differences, for example, in same-species comparisons. Comparisons between different mice strains suggest that the IF is consistent enough to detect these differences. Nevertheless, the reliability of the method has not yet been examined directly. METHOD In this study, we evaluate the reliability of the method for the determination of cellular and neuronal numbers of Swiss mice. We performed repeated cell counts of the same material by different experimenters to quantify different sources of variation. RESULTS In total cell counts, we observed that for the cerebral cortex most of the variance was at the counter level. For the cerebellum, most of the variance is attributed to the sample itself. As for neurons, random error along with the immunostaining correspond to most of the variation, both in the cerebral cortex and in the cerebellum. Test-retest reliability coefficients were relatively high, especially for cell counts. CONCLUSIONS Although biases between counters and random variation in staining could be problematic when aggregating data from different sources, we offer practical suggestions to improve the reliability of the method. While small, this study is a most needed step towards more precise measurement of the brain's cellular composition.
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21
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Xu SY, Zhang QL, Zhang Q, Wan L, Jiang J, Tu T, Manavis J, Pan A, Cai Y, Yan XX. Regional and Cellular Mapping of Sortilin Immunoreactivity in Adult Human Brain. Front Neuroanat 2019; 13:31. [PMID: 30914927 PMCID: PMC6422922 DOI: 10.3389/fnana.2019.00031] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 02/21/2019] [Indexed: 11/16/2022] Open
Abstract
Sortilin is a member of the vacuolar protein sorting 10 protein (VPS10P) domain receptor family, which carries out signal transduction and protein transport in cells. Sortilin serves as the third, G-protein uncoupled, receptor of neurotensin that can modulate various brain functions. More recent data indicate an involvement of sortilin in mood disorders, dementia and Alzheimer-type neuropathology. However, data regarding the normal pattern of regional and cellular expression of sortilin in the human brain are not available to date. Using postmortem adult human brains free of neuropathology, the current study determined sortilin immunoreactivity (IR) across the entire brain. Sortilin IR was broadly present in the cerebrum and subcortical structures, localizing to neurons in the somatodendritic compartment, but not to glial cells. In the cerebrum, sortilin IR exhibited differential regional and laminar patterns, with pyramidal, multipolar and polymorphic neurons in cortical layers II–VI, hippocampal formation and amygdaloid complex more distinctly labeled relative to GABAergic interneurons. In the striatum and thalamus, numerous small-to-medium sized neurons showed light IR, with a small group of large sized neurons heavily labeled. In the midbrain and brainstem, sortilin IR was distinct in neurons at the relay centers of descending and ascending neuroanatomical pathways. Dopaminergic neurons in the substantia nigra, cholinergic neurons in the basal nuclei of Meynert and noradrenergic neurons in the locus coeruleus co-expressed strong sortilin IR in double immunofluorescence. In comparison, sortilin IR was weak in the olfactory bulb and cerebellar cortex, with the mitral and Purkinje cells barely visualized. A quantitative analysis was carried out in the lateral, basolateral, and basomedial nuclei of the amygdaloid complex, as well as cortical layers II–VI, which established a positive correlation between the somal size and the intensity of sortilin IR among labeled neurons. Together, the present study demonstrates a predominantly neuronal expression of sortilin in the human brain with substantial regional and cell-type variability. The enriched expression of sortilin in pyramidal, dopaminergic, noradrenergic and cholinergic neurons suggests that this protein may be particularly required for signal transduction, protein trafficking and metabolic homeostasis in populations of relatively large-sized projective neurons.
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Affiliation(s)
- Shu-Yin Xu
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Qi-Lei Zhang
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Qi Zhang
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Lily Wan
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Juan Jiang
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Tian Tu
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Jim Manavis
- SA Pathology, Schools of Medicine and Veterinary Science, Hanson Institute Centre for Neurological Diseases, The University of Adelaide, Adelaide, SA, Australia
| | - Aihua Pan
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China.,Center for Morphological Sciences, School of Basic Medicine, Central South University, Changsha, China
| | - Yan Cai
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China.,Department of Histology and Embryology, Xiangya School of Medicine, Central South University, Changsha, China
| | - Xiao-Xin Yan
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Xiangya Hospital, Central South University, Changsha, China
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22
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Valério-Gomes B, Guimarães DM, Szczupak D, Lent R. The Absolute Number of Oligodendrocytes in the Adult Mouse Brain. Front Neuroanat 2018; 12:90. [PMID: 30425626 PMCID: PMC6218541 DOI: 10.3389/fnana.2018.00090] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 10/11/2018] [Indexed: 12/12/2022] Open
Abstract
The central nervous system is a highly complex network composed of various cell types, each one with different subpopulations. Each cell type has distinct roles for the functional operation of circuits, and ultimately, for brain physiology in general. Since the absolute number of each cell type is considered a proxy of its functional complexity, one approach to better understand how the brain works is to unravel its absolute cellularity and the quantitative relations between cell populations; in other words, how one population of cells is quantitatively structured, in relation to another. Oligodendrocytes are one of these cell types - mainly, they provide electric insulation to axons, optimizing action potential conduction. Their function has recently been revisited and their role extended, one example being their capability of providing trophic support to long axons. To determine the absolute cellularity of oligodendroglia, we have developed a protocol of oligodendrocyte quantification using the isotropic fractionator with a pan-marker for this cell type. We report a detailed assessment of specificity and universality of the oligodendrocyte transcription factor 2 (Olig2), through systematic confocal analyses of the C57BL/6 mouse brain. In addition, we have determined the absolute number (17.4 million) and proportion (about 20%) of this cell type in the brain (and in different brain regions), and tested if this population, at the intraspecific level, scales with the number of neurons in an allometric-based approach. Considering these numbers, oligodendrocytes proved to be the most numerous of glial cells in the mouse brain.
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Affiliation(s)
- Bruna Valério-Gomes
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Daniel M Guimarães
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Diego Szczupak
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Roberto Lent
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.,D'Or Institute for Research and Education, Rio de Janeiro, Brazil
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23
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Dos Santos SE, Porfirio J, da Cunha FB, Manger PR, Tavares W, Pessoa L, Raghanti MA, Sherwood CC, Herculano-Houzel S. Cellular Scaling Rules for the Brains of Marsupials: Not as "Primitive" as Expected. BRAIN, BEHAVIOR AND EVOLUTION 2017; 89:48-63. [PMID: 28125804 DOI: 10.1159/000452856] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 10/19/2016] [Indexed: 11/19/2022]
Abstract
In the effort to understand the evolution of mammalian brains, we have found that common relationships between brain structure mass and numbers of nonneuronal (glial and vascular) cells apply across eutherian mammals, but brain structure mass scales differently with numbers of neurons across structures and across primate and nonprimate clades. This suggests that the ancestral scaling rules for mammalian brains are those shared by extant nonprimate eutherians - but do these scaling relationships apply to marsupials, a sister group to eutherians that diverged early in mammalian evolution? Here we examine the cellular composition of the brains of 10 species of marsupials. We show that brain structure mass scales with numbers of nonneuronal cells, and numbers of cerebellar neurons scale with numbers of cerebral cortical neurons, comparable to what we have found in eutherians. These shared scaling relationships are therefore indicative of mechanisms that have been conserved since the first therians. In contrast, while marsupials share with nonprimate eutherians the scaling of cerebral cortex mass with number of neurons, their cerebella have more neurons than nonprimate eutherian cerebella of a similar mass, and their rest of brain has fewer neurons than eutherian structures of a similar mass. Moreover, Australasian marsupials exhibit ratios of neurons in the cerebral cortex and cerebellum over the rest of the brain, comparable to artiodactyls and primates. Our results suggest that Australasian marsupials have diverged from the ancestral Theria neuronal scaling rules, and support the suggestion that the scaling of average neuronal cell size with increasing numbers of neurons varies in evolution independently of the allocation of neurons across structures.
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Affiliation(s)
- Sandra E Dos Santos
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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24
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von Bartheld CS, Bahney J, Herculano-Houzel S. The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting. J Comp Neurol 2016; 524:3865-3895. [PMID: 27187682 PMCID: PMC5063692 DOI: 10.1002/cne.24040] [Citation(s) in RCA: 566] [Impact Index Per Article: 70.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 05/13/2016] [Accepted: 05/16/2016] [Indexed: 12/13/2022]
Abstract
For half a century, the human brain was believed to contain about 100 billion neurons and one trillion glial cells, with a glia:neuron ratio of 10:1. A new counting method, the isotropic fractionator, has challenged the notion that glia outnumber neurons and revived a question that was widely thought to have been resolved. The recently validated isotropic fractionator demonstrates a glia:neuron ratio of less than 1:1 and a total number of less than 100 billion glial cells in the human brain. A survey of original evidence shows that histological data always supported a 1:1 ratio of glia to neurons in the entire human brain, and a range of 40-130 billion glial cells. We review how the claim of one trillion glial cells originated, was perpetuated, and eventually refuted. We compile how numbers of neurons and glial cells in the adult human brain were reported and we examine the reasons for an erroneous consensus about the relative abundance of glial cells in human brains that persisted for half a century. Our review includes a brief history of cell counting in human brains, types of counting methods that were and are employed, ranges of previous estimates, and the current status of knowledge about the number of cells. We also discuss implications and consequences of the new insights into true numbers of glial cells in the human brain, and the promise and potential impact of the newly validated isotropic fractionator for reliable quantification of glia and neurons in neurological and psychiatric diseases. J. Comp. Neurol. 524:3865-3895, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
| | - Jami Bahney
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Suzana Herculano-Houzel
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, and Instituto Nacional de Neurociência Translacional, CNPq/MCT, Brasil
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25
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von Bartheld CS, Bahney J, Herculano-Houzel S. The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting. J Comp Neurol 2016; 524:3865-3895. [PMID: 27187682 DOI: 10.1002/cne.2404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 05/13/2016] [Accepted: 05/16/2016] [Indexed: 05/25/2023]
Abstract
For half a century, the human brain was believed to contain about 100 billion neurons and one trillion glial cells, with a glia:neuron ratio of 10:1. A new counting method, the isotropic fractionator, has challenged the notion that glia outnumber neurons and revived a question that was widely thought to have been resolved. The recently validated isotropic fractionator demonstrates a glia:neuron ratio of less than 1:1 and a total number of less than 100 billion glial cells in the human brain. A survey of original evidence shows that histological data always supported a 1:1 ratio of glia to neurons in the entire human brain, and a range of 40-130 billion glial cells. We review how the claim of one trillion glial cells originated, was perpetuated, and eventually refuted. We compile how numbers of neurons and glial cells in the adult human brain were reported and we examine the reasons for an erroneous consensus about the relative abundance of glial cells in human brains that persisted for half a century. Our review includes a brief history of cell counting in human brains, types of counting methods that were and are employed, ranges of previous estimates, and the current status of knowledge about the number of cells. We also discuss implications and consequences of the new insights into true numbers of glial cells in the human brain, and the promise and potential impact of the newly validated isotropic fractionator for reliable quantification of glia and neurons in neurological and psychiatric diseases. J. Comp. Neurol. 524:3865-3895, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
| | - Jami Bahney
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Suzana Herculano-Houzel
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, and Instituto Nacional de Neurociência Translacional, CNPq/MCT, Brasil
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Sobrero R, Fernández-Aburto P, Ly-Prieto Á, Delgado SE, Mpodozis J, Ebensperger LA. Effects of Habitat and Social Complexity on Brain Size, Brain Asymmetry and Dentate Gyrus Morphology in Two Octodontid Rodents. BRAIN, BEHAVIOR AND EVOLUTION 2016; 87:51-64. [DOI: 10.1159/000444741] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 02/17/2016] [Indexed: 11/19/2022]
Abstract
Navigational and social challenges due to habitat conditions and sociality are known to influence dentate gyrus (DG) morphology, yet the relative importance of these factors remains unclear. Thus, we studied three natural populations of O. lunatus (Los Molles) and Octodon degus (El Salitre and Rinconada), two caviomorph species that differ in the extent of sociality and with contrasting vegetation cover of habitat used. The brains and DG of male and female breeding degus with simultaneous information on their physical and social environments were examined. The extent of sociality was quantified from total group size and range area overlap. O. degus at El Salitre was more social than at Rinconada and than O. lunatus from Los Molles. The use of transects to quantify cover of vegetation (and other physical objects in the habitat) and measures of the spatial behavior of animals indicated animal navigation based on unique cues or global landmarks is more cognitively challenging to O. lunatus. During lactation, female O. lunatus had larger brains than males. Relative DG volume was similar across sexes and populations. The right hemisphere of male and female O. lunatus had more cells than the left hemisphere, with DG directional asymmetry not found in O. degus. Degu population differences in brain size and DG cell number seemed more responsive to differences in habitat than to differences in sociality. Yet, large-sized O. degus (but not O. lunatus) that ranged over larger areas and were members of larger social groups had more DG cells per hemisphere. Thus, within-population variation in DG cell number by hemisphere was consistent with a joint influence of habitat and sociality in O. degus at El Salitre.
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