Phylogenetic variation of layer II cortical immature neurons in dog and horse confirms covariance with brain size and neocortical surface.
Abstract: Recent research in brain structural plasticity has identified "immature" or "dormant" neurons in layer II of the cerebral cortex (cortical immature neurons; cINs), cells that remain in a prolonged state of arrested development but retain the ability to resume maturation and integrate functionally into mature cortical circuits. These immature cells are far more abundant in large-brained mammals, being restricted to paleocortex (piriform cortex) in small-brained rodents and extending in the widely expanded neocortical mantle of species with large gyrencephalic brains. In a previous systematic analysis, using a comparable method for quantification in eight mammalian species, including mice, chimpanzees, and others of diverse phylogenetic backgrounds and neuroanatomical structure, cIN density showed covariation with brain size. Notably, however, members of the order Carnivora (cats and foxes) displayed the highest cIN densities with respect to sheep and chimpanzees, endowed with larger brains. Here we used the same method to characterize and quantify the cINs in the cerebral cortex of dogs (carnivores) and horses (herbivores with a very large brain) to investigate the position of these two species in the phylogenetic variation. Our results further strengthen the finding of covariance between cIN density and increasing brain size and confirm a relationship with neocortical expansion. These results support the emerging view that immature or dormant neurons may represent a reservoir of undifferentiated (stem cell-independent) neuronal cells for the widely expanded cortices of mammals endowed with high order cognitive functions.
© 2025. The Author(s).
Publication Date: 2025-07-07 PubMed ID: 40622463PubMed Central: PMC12234597DOI: 10.1007/s00429-025-02981-xGoogle Scholar: Lookup
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Summary
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The research examines the correlation between the amount of dormant neurons in the brain’s second cortical layer and the size of the brain in various animal species. A higher number of these neurons were found in animals with larger brains, such as dogs and horses.
Background and Objective
- The focus of the research lies on “immature” or “dormant” neurons located in the second layer of the cerebral cortex. These neuronal cells stay in a state of delayed development but can restart their maturation process and become integrated into mature neural circuits.
- The study seeks to characterize and quantify these cortical immature neurons in the brains of dogs and horses and compare them to other mammals in order to further understand the correlation of these neuron densities with brain size and phylogenetic differences.
Findings and Significance
- The research reveals that these cortical immature neurons are more prevalent in larger-brained mammals and consistently distributed in relation to the brain’s size. Particularly, the study points out that members of the order Carnivora such as cats and dogs and large-brained herbivores like horses possess the highest densities of these neuronal cells.
- The results of the research reaffirm the correlation between the density of cortical immature neurons and an increasing brain size. More so, the evidence suggests a link between these neuron densities and the expansion of the neocortex—a larger area of the brain associated with higher cognitive functions.
- This study contributes to the fundamental understanding of brain structural plasticity in relation to brain size across different species. It supports the emerging belief that these immature neurons could potentially serve as a source of undifferentiated (non-stem cell dependent) neuronal cells for the extended cortices in mammals with advanced cognitive functions.
Cite This Article
APA
Pattaro A, Ghibaudi M, Corrente C, Telitsyn N, Graic JM, Aresu L, Sherwood CC, Bonfanti L.
(2025).
Phylogenetic variation of layer II cortical immature neurons in dog and horse confirms covariance with brain size and neocortical surface.
Brain Struct Funct, 230(6), 115.
https://doi.org/10.1007/s00429-025-02981-x Publication
Researcher Affiliations
- Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy.
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095, Turin, Grugliasco (TO), Italy.
- Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy.
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095, Turin, Grugliasco (TO), Italy.
- Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy.
- Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy.
- Department of Comparative Biomedicine and Food Science, University of Padova, Legnaro, Padova, Italy.
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095, Turin, Grugliasco (TO), Italy.
- Department of Anthropology and Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington DC, USA.
- Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy. luca.bonfanti@unito.it.
- Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095, Turin, Grugliasco (TO), Italy. luca.bonfanti@unito.it.
MeSH Terms
- Animals
- Phylogeny
- Neocortex / cytology
- Dogs / anatomy & histology
- Horses / anatomy & histology
- Neurons / cytology
- Neurons / physiology
- Organ Size
- Cerebral Cortex / cytology
- Male
- Brain / anatomy & histology
- Species Specificity
- Female
- Cell Count
- Neural Stem Cells / cytology
Grant Funding
- 67935-2021.2174 / Compagnia di San Paolo
- RF=2022.0618 / Fondazione CRT - Cassa di Risparmio di Torino
- 2022LB4X3N / Ministero dell'Istruzione e del Merito
Conflict of Interest Statement
Declarations. Competing interest: The authors declare that they have no competing interests.
References
This article includes 84 references
- Aboitiz F, Montiel JF. Olfaction, navigation, and the origin of isocortex. Front Neurosci 9:402.
- Andrews EF, Pascalau R, Horowitz A, Lawrence GM, Johnson PJ. Extensive connections of the canine olfactory pathway revealed by tractography and dissection. J Neurosci 42(33):6392–6407.
- Bao H, Song J. Treating brain disorders by targeting adult neural stem cells. Trends Mol Med 24(12):991–1006.
- Barone R, Bortolami R. Anatomia comparata dei mammiferi domestici—Neurologia—Sistema nervoso centrale. Edagricole, Milan, Italy. Pag 480–481.
- Beall MJ, Lewis DA. Heterogeneity of layer II neurons in human entorhinal cortex. J Comp Neurol 321(2):241–266.
- Benedetti B, Dannehl D, König R, Coviello S, Kreutzer C, Zaunmair P, Jakubecova D, Weiger TM, Aigner L, Nacher J, Engelhardt M, Couillard-Després S. Functional integration of neuronal precursors in the adult murine piriform cortex. Cereb Cortex 30(3):1499–1515.
- Benedetti B, Couillard-Després S. Why would the brain need dormant neuronal precursors?. Front Neurosci 16:877167.
- Benedetti B, Reisinger M, Hochwartner M, Gabriele G, Jakubecova D, Benedetti A, Bonfanti L, Couillard-Després S. The awakening of dormant neuronal precursors in the adult and aged brain. Aging Cell 22:e13974.
- Bond AM, Ming G, Song H. Adult mammalian neural stem cells and neurogenesis: five decades later. Cell Stem Cell 17:385–395.
- Bonfanti L, Nacher J. New scenarios for neuronal structural plasticity in non-neurogenic brain parenchyma: the case of cortical layer II immature neurons. Prog Neurobiol 98:1–15.
- Bonfanti L, Seki T. The PSA-NCAM-positive “immature” neurons: an old discovery providingnew vistas on brain structural plasticity. Cells 10:2542.
- Bonfanti L, Charvet CJ. Brain plasticity in humans and model systems: advances, challenges, and future directions. Int J Mol Sci 22:9358.
- Bonfanti L, La Rosa C, Ghibaudi M, Sherwood CC. Adult neurogenesis and “immature” neurons in mammals: an evolutionary trade-off in plasticity?. Brain Struct Funct 229(8):1775–1793.
- Brecht M. Large brains: big unknowns in cellular neuroscience. Curr Op Neurobiol 91:102981.
- Brown JP, Couillard-Despres S, Cooper-Kuhn CM, Winkler J, Aigner L, Kuhn HG. Transient expression of doublecortin during adult neurogenesis. J Comp Neurol 467:1–10.
- Cai Y, Xiong K, Chu Y, Luoc D-W, Luoa X-G, Yuanc X-Y, Strubled RG, Cloughe RW, Spencer DD, Williamson A, Kordowerb JH, Patrylog PR, Yan X-X. Doublecortin expression in adult cat and primate cerebral cortex relates to immature neurons that develop into GABAergic subgroups. Exp Neurol 216(2):342–356.
- Chédotal A. Development and plasticity of commissural circuits: from locomotion to brain repair. Trends Neurosci 37:551–562.
- Cipriani S, Ferrer A, Arinica I, Kovacs G, Verney C, Nardelli J, Khung S, Delezoide AL, Milenkovic I, Rasika S, Manivet P, Benifla JL, Deriot N, Gressens P, Adle-Biassette H. Hippocampal radial glial subtypes and their neurogenic potential in human fetuses and healthy and Alzheimer disease adults. Cereb Cortex 28:2458–2478.
- Coviello S, Benedetti B, Jakubecova D, Belles M, Klimczak P, Gramuntell Y, Couillard-Despres S, Nacher J. PSA depletion induces the differentiation of immature neurons in the piriform cortex of adult mice. Int J Mol Sci 22:5733.
- Coviello S, Gramuntell Y, Klimczak P, Varea E, Blasco-Ibañez JM, Crespo C, Gutierrez A, Nacher J. Phenotype and distribution of immature neurons in the human cerebral cortex layer II. Front Neuroanat 16:851432.
- Cozzi B, Povinelli M, Ballarin C, Granato A. The brain of the horse: weight and cephalization quotients. Brain Behav Evol 83:9–16.
- Cushman JD, Drew MR, Krasne FB. The environmental sculpting hypothesis of juvenile and adult hippocampal neurogenesis. Prog Neurobiol 199:101961.
- de Sousa AA, Rigby Dames BA, Graff EC, Mohamedelhassan R, Vassilopoulos T, Charvet CJ. Going beyond established model systems of Alzheimer’s disease: companion animals provide novel insights into the neurobiology of aging. Commun Biol 6(1):655.
- Dewey CW, da Costa RC. Canine brain atlas. In: Practical guide to canine and feline neurology, 3rd edition, Wiley-Blackwell, pp 633–649.
- Duque A, Arellano JI, Rakic P. An assessment of the existence of adult neurogenesis in humans and value of its rodent models for neuropsychiatric diseases. Mol Psychiatr 27(1):377–382.
- Feliciano DM, Bordey A, Bonfanti L. Noncanonical sites of adult neurogenesis in the mammalian brain. Cold Spr Harbor Perspect Biol 7:a018846.
- Galakhova AA, Hunt S, Wilbers R, Heyer DB, de Kock CP, Mansvelder HD, Goriounova NA. Evolution of cortical neurons supporting human cognition. Trends Cogn Sci 26:909–922.
- Ghibaudi M, Amenta A, Agosti M, Riva M, Graïc J-M, Bifari F, Bonfanti L. Consistency and variation in doublecortin and Ki67 antigen detection in the brain tissue of different mammals, including humans. Int J Mol Sci 24:2514.
- Ghibaudi M, Marchetti N, Vergnano E, La Rosa C, Benedetti B, Couillard-Despres S, Farioli-Vecchioli S, Bonfanti L. Age-related changes in layer II immature neurons of the murine piriform cortex. Front Cell Neurosci 17:1205173.
- Ghibaudi M, Boda E, Bonfanti L. From mice to humans: a need for comparable results in mammalian neuroplasticity. Neural Regen Res 20:464–466.
- Ghibaudi M, Zanone A, Bonfanti L. Brain structural plasticity in large-brained mammals: not only narrowing roads. Neural Reg Res Online ahead of print.
- Gleeson JG, Lin PT, Flanagan LA, Walsh CA. Doublecortin is a microtubule-associated protein and is expressed widely by migrating neurons. Neuron 23:257–271.
- Gómez-Climent MA, Castillo-Gómez E, Varea E, Guirado R, Blasco-Ibáñez JM, Crespo C, Martínez-Guijarro FJ, Nácher J. A population of prenatally generated cells in the rat paleocortex maintains an immature neuronal phenotype into adulthood. Cereb Cortex 18:2229–2240.
- Grewal JS, Gloe T, Hegedus J, Bitterman K, Billings BK, Chengetanai S, Bentil S, Wang VX, Ng JC, Tang CY, Geletta S, Wicinski B, Bertelson M, Tendler BC, Rogier B, Mars RB, Aguirre GK, Rusbridge C, Hof PR, Sherwood CC, Manger PR, Spocter MA. Brain gyrification in wild and domestic canids: Has domestication changed the gyrification index in domestic dogs?. J Comp Neurol 528(18):3209–3228.
- Gusel’nikova VV, Korzhevskiy DE. NeuN as a neuronal nuclear antigen and neuron differentiation marker. Acta Naturae 7:42–47.
- Hecht EE, Barton SA, Rogers Flattery CN, Meza Meza A. The evolutionary neuroscience of domestication. Trends Cogn Sci 27(6):553–567.
- Herculano-Houzel S. Numbers of neurons as biological correlates of cognitive capability. Curr Op Behav Sci 16:1–7.
- Heyer DB, Wilbers R, Galakhova AA, Hartsema E, Braak S, Hunt S, Verhoog MB, Muijtjens ML, Mertens EJ, Idema S, Baayen JC, de Witt Hamer P, Klein M, McGraw M, Lein ES, de Kock CPJ, Mansvelder HD, Goriounova NA. Verbal and general IQ associate with supragranular layer thickness and cell properties of the left temporal cortex. Cereb Cortex 32:2343–2357.
- Hutsler JJ, Lee DG, Porter KK. Comparative analysis of cortical layering and supragranular layer enlargement in rodent carnivore and primate species. Brain Res 1052:71–81.
- Johnson PJ, Janvier V, Luh W-M, FitzMaurice M, Southard T, Barry EF. Equine stereotaxtic population average brain atlas with neuroanatomic correlation. Front Neuroanat 13:89.
- Kee N, Sivalingam S, Boonstra R, Wojtowicz JM. The utility of Ki-67 and BrdU as proliferative markers of adult neurogenesis. J Neurosci Meth 115:97–105.
- Kempermann G. Environmental enrichment, new neurons and the neurobiology of individuality. Nat Rev Neurosci 20(4):235–245.
- König R, Benedetti B, Rotheneichner P, O’Sullivan A, Kreutzer C, Belles M, Nacher J, Weiger TM, Aigner L, Couillard-Després S. Distribution and fate of DCX/PSA-NCAM expressing cells in the adult mammalian cortex: a local reservoir for adult cortical neuroplasticity?. Front Biol 11:193–213.
- Krubitzer L. In search of a unifying theory of complex brain evolution. Ann NY Acad Sci 1156:44–67.
- Krubitzer LA, Seelkea AMH. Cortical evolution in mammals: The bane and beauty of phenotypic variability. Proc Natl Acad Sci USA 109:10647–10654.
- Kumar S, Stecher G, Suleski M, Hedges SB. TimeTree: a resource for timelines, timetrees, and divergence times. Mol Biol Evol 34:1812–1819.
- La Rosa C, Parolisi R, Bonfanti L. Brain structural plasticity: From adult neurogenesis to immature neurons. Front Neurosci 14:75.
- La Rosa C, Cavallo F, Pecora A, Chincarini M, Ala U, Faulkes CG, Nacher J, Cozzi B, Sherwood CC, Amrein I, Bonfanti L. Phylogenetic variation in cortical layer II immature neuron reservoir of mammals. eLife 9:e55456.
- La Rosa C, Bonfanti L. Searching for alternatives to brain regeneration. Neural Regen Res 16(11):2198–2200.
- La Rosa C, Ghibaudi M, Bonfanti L. Newly generated and non-newly generated “immature” neurons in the mammalian brain: A possible reservoir of young cells to prevent brain aging and disease?. J Clin Med 8(5):685.
- Lea SEG, Osthaus B. In what sense are dogs special? Canine cognition in comparative context. Learn Behav 46:335–363.
- Li Y-N, Hu D-D, Cai X-L, Wang Y, Yang C, Jiang J, Zhang Q-L, Tu T, Wang X-S, Wang H. Doublecortin expressing neurons in human cerebral cortex layer II and amygdala from infancy to 100 year-old. Mol Neurobiol 60(6):3464–3485.
- Li Y, Wang G-D, Wang M-S, Irwin DM, Wu D-D, Zhang Y-P. Domestication of the dog from the wolf was promoted by enhanced excitatory synaptic plasticity: a hypothesis. Genome Biol Evol 6(11):3115–3121.
- Lim DA, Alvarez-Buylla A. The adult ventricular-subventricular zone (V-SVZ) and olfactory bulb (OB) neurogenesis. Cold Spr Harb Perspect Biol 8:a018820.
- Lindvall O, Kokaia Z. Stem cells in human neurodegenerative disorders—time for clinical translation?. J Clin Invest 120(1):29–40.
- Luzzati F, Bonfanti L, Fasolo A, Peretto P. DCX and PSA-NCAM expression identifies a population of neurons preferentially distributed in associative areas of different pallial derivatives and vertebrate species. Cereb Cortex 19:1028–1041.
- Marin-Padilla M. Cajal-Retzius cells and the development of the neocortex. Trends Neurosci 21:64–71.
- McEwen BS. In pursuit of resilience: stress, epigenetics, and brain plasticity. Ann NY Acad Sci 1373(1):56–64.
- Myers P, Espinosa R, Parr CS, Jones T, Hammond GS, Dewey TA. The animal diversity web. https://animaldiversity.org.
- Mullen RJ, Buck CR, Smith AM. NeuN, a neuronal specific nuclear protein in vertebrates. Development 116:201–211.
- Naumann RK, Preston-Ferrer P, Brecht M, Burgalossi A. Structural modularity and grid activity in the medial entorhinal cortex. J Neurophysiol 119:2129–2144.
- Naumann RK, Ray S, Prokop S, Las L, Heppner FL, Brecht M. Conserved size and periodicity of pyramidal patches in layer 2 of medial/caudal entorhinal cortex. J Comp Neurol 524:783–806.
- Nitzsche B, Boltze J, Ludewig E, Flegel T, Schmidt MJ, Seeger J, Barthel H, Brooks OW, Gounis MJ, Stoffel MH, Schulze S. A stereotaxic breed-averaged, symmetric T2w canine brain atlas including detailed morphological and volumetrical data sets. Neuroimage 187:93–103.
- Palazzi X, Pardo ID, Ritenour H, Rao DB, Bolon B, Garman RH. A technical guide to sampling the Beagle dog nervous system for general toxicity and neurotoxicity studies. Toxicol Pathol 50(4):432–465.
- Palazzo O, La Rosa C, Piumatti M, Bonfanti L. Do large brains of long-living mammals prefer non-newly generated, immature neurons?. Neural Regen Res 13:633–634.
- Parolisi R, Cozzi B, Bonfanti L. Humans and dolphins: Decline and fall of adult neurogenesis. Front Neurosci 12:497.
- Patzke N, Spocter MA, Karlsson KÆ, Bertelsen MF, Haagensen M, Chawana R, Streicher S, Kaswera C, Gilissen E, Alagaili AN, Mohammed OB, Reep RL, Bennett NC, Siegel JM, Ihunwo AO, Manger PR. In contrast to many other mammals, cetaceans have relatively small hippocampi that appear to lack adult neurogenesis. Brain Struct Funct 220(1):361–383.
- Penso-Dolfin L, Moxon S, Haerty W, Di Palma F. The evolutionary dynamics of microRNAs in domestic mammals. Sci Rep 8:17050.
- Piumatti M, Palazzo O, La Rosa C, Crociara P, Parolisi R, Luzzati F, Levy F, Bonfanti L. Non-newly generated, “immature” neurons in the sheep brain are not restricted to cerebral cortex. J Neurosci 38(4):826–842.
- Rørvang MV, Nielsen BL, McLean AN. Sensory abilities of horses and their importance for equitation science. Front Vet Sci 7:633.
- Rosenzweig MR, Bennett EL. Psychobiology of plasticity: effects of training and experience on brain and behavior. Behav Brain Res 78:57–65.
- Roth G, Dicke U. Evolution of the brain and intelligence. Trends Cogn Sci 9:250–257.
- Rotheneichner P, Belles M, Benedetti B, König R, Dannehl D, Kreutzer C, Zaunmair P, Engelhardt M, Aigner L, Nacher J, Couillard-Després S. Cellular plasticity in the adult murine piriform cortex: continuous maturation of dormant precursors into excitatory neurons. Cereb Cortex 28:2610–2621.
- Ruple A, MacLean E, Snyder-Mackler N, Creevy KE, Promislow D. Dog models of aging. Annu Rev Anim Biosci 10:419–39.
- Sanai N, Nguyen T, Ihrie RA, Mirzadeh Z, Tsai H-H, Wong M, Gupta N, Berger MS, Huang E, Garcia-Verdugo JM, Rowitch DH, Alvarez-Buylla A. Corridors of migrating neurons in the human brain and their decline during infancy. Nature 478:382–386.
- Semënov MV. Adult hippocampal neurogenesis is a developmental process involved in cognitive development. Front Neurosci 13:159.
- Shepherd GM, Rowe TB. Neocortical lamination: insights from neuron types and evolutionary precursors. Front Neuroanat 11:100.
- Snyder JS. Recalibrating the relevance of adult neurogenesis. Trends Neurosci 42:164–178.
- Stern Y. An approach to studying the neural correlates of reserve. Brain Imag Behav 11:410–416.
- Sorrells SF, Paredes MF, Cebrian-Silla A, Sandoval K, Qi D, Kelley KW. Human hippocampal neurogenesis drops sharplyin children to undetectable levels in adults. Nature 555:377-381.
- Stuckenschneider K, Hellige M, Feige K, Gasse H. 3-Tesla magnetic resonance imaging of the equine brain in healthy horses—potentials and limitations. Pferdeheilkunde 30:657–670.
- Takeuchi T, Sugita S. Histological atlas and morphological features by Nissl staining in the amygdaloid complex of the horse, cow and pig. J Equine Sci 18(1):13–25.
- Wilson DE, Reeder DM. Mammal species of the world: a taxonomic and geographic reference. Third edition. Johns Hopkins University Press, Baltimore, Maryland, p 2142, ISBN 0-8018-8221-4.
- Zilles K, Palomero-Gallagher N, Amunts K. Development of cortical folding during evolution and ontogeny. Trends Neurosci 36:275–284.
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