Yuan Wang a,b,1, Agnieszka Brzozowska-Prechtl a, and Harvey J. Karten a
-Author Affiliations
aDepartment of Neurosciences, School of Medicine, University of California San Diego, La Jolla, CA 92093-0608; and
bDepartment of Otolaryngology and Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA 98195-7923
Communicated by Melvin I. Simon, California Institute of Technology, Pasadena, CA, June 2, 2010 (received for review January 27, 2010)
Abstract
The mammalian neocortex mediates complex cognitive behaviors, such as sensory perception, decision making, and language. The evolutionary history of the cortex, and the cells and circuitry underlying similar capabilities in nonmammals, are poorly understood, however. Two distinct features of the mammalian neocortex are lamination and radially arrayed columns that form functional modules, characterized by defined neuronal types and unique intrinsic connections. The seeming inability to identify these characteristic features in nonmammalian forebrains with earlier methods has often led to the assumption of uniqueness of neocortical cells and circuits in mammals. Using contemporary methods, we demonstrate the existence of comparable columnar functional modules in laminated auditory telencephalon of an avian species (Gallus gallus). A highly sensitive tracer was placed into individual layers of the telencephalon within the cortical region that is similar to mammalian auditory cortex. Distribution of anterograde and retrograde transportable markers revealed extensive interconnections across layers and between neurons within narrow radial columns perpendicular to the laminae. This columnar organization was further confirmed by visualization of radially oriented axonal collaterals of individual intracellularly filled neurons. Common cell types in birds and mammals that provide the cellular substrate of columnar functional modules were identified. These findings indicate that laminar and columnar properties of the neocortex are not unique to mammals and may have evolved from cells and circuits found in more ancient vertebrates. Specific functional pathways in the brain can be analyzed in regard to their common phylogenetic origins, which introduces a previously underutilized level of analysis to components involved in higher cognitive functions.
neocortex evolution columnar organization primary auditory cortex intrinsic circuitry granule cell
Footnotes
1To whom correspondence should be addressed. E-mail: wangyuan@uw.edu.
Author contributions: Y.W. and H.K. designed research; Y.W. and A.B.-P. performed research; Y.W. and H.K. analyzed data; and Y.W. and H.K. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1006645107/-/DCSupplemental.
*A vertebrate brain has three primary portions: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain), with the prosencephalon consisting of the telencephalon and diencephalon. The mammalian telencephalon contains cerebral cortex (traditionally and simplistically considered to consist of two major divisions, the neocortex and allocortex), claustrum, amygdala, and basal ganglia. The first three components are derived from the pallial sector of the developing telencephalon, whereas the basal ganglion is developed from the subpallial sector. In nonmammalian species, the pallial portion of the telencephalon is also divided into hyperpallium, mesopallium, and nidopallium based on location.
†Dugas-Ford J, Ragsdale CW, Nuclei in the avian dorsal ventricular ridge share molecular similarities with specific layers of the mammalian neocortex. Society for Neuroscience annual meeting, Oct. 23–27, 2004, San Diego, CA (abstr).
‡Dugas-Ford J, Ragsdale CW, Markers of mammalian layer 5 and 6 cells demonstrate the subnuclear architecture of the avian arcopallium. Society for Neuroscience annual meeting, Oct. 17–21, 2009, Chicago, lL (abstr).
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PDF grátis aqui.
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NOTA DESTE BLOGGER:
Lembra de expressão -- "Fulano tem miolos de passarinho"? Taí, a ciência confirma o bom senso: nós mamíferos temos miolos de passarinhos! Quais são as implicações ou dificuldades que esta pesquisa trás para a teoria da evolução através da seleção natural?
“a comparable region in the brains of chickens concerned with analyzing auditory inputs is constructed similarly to that of mammals.”
“They discovered that the avian cortical region was also composed of laminated layers of cells linked by narrow, radial columns of different types of cells with extensive interconnections that form microcircuits that are virtually identical to those found in the mammalian cortex.”
Problemas???
“But this kind of thinking presented a serious problem for neurobiologists trying to figure out the evolutionary origins of the mammalian cortex,” ...
“Namely, where did all of that complex circuitry come from and when did it first evolve?”
... “the beginnings of an answer: From an ancestor common to both mammals and birds that dates back at least 300 million years.”
E as propriedades das células laminar e colunar no neocórtex “evolved from cells and circuits in much more ancient vertebrates.” Como evoluíram os autores não disseram, só disseram que evoluíram...
Uau!!! A evolução é mesmo muito mais inteligente do que você idiota: isso é um exemplo nítido de evolução convergente. Por que não eu não tive esta ideia brilhante antes, pois segundo a pesquisa, as aves estão em um “parallel branch to mammals on the evolutionary tree”.
QED/Alakazam/e Darwin estava certo: os resultados de semelhança somente poderiam ocorrer através de evolução convergente.
Fui, nem sei por que, pensando como que a Lógica Darwiniana 101 é facinha, facinha...
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