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Start Over Author "Nikola T. Markov" Topic 0302 clinical medicine
5 results on '"Nikola T. Markov"'

1. Unique Features of Subcortical Circuits in a Macaque Model of Congenital Blindness

Author

Henry Kennedy, Kenneth Knoblauch, Nikola T. Markov, Loïc Magrou, Pascal Barone, Michel Berland, Gwylan Scheeren, Pascale Giroud, Colette Dehay, Herbert P. Killackey, Institut cellule souche et cerveau (U846 Inserm - UCBL1), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre de recherche cerveau et cognition (CERCO), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut des sciences du cerveau de Toulouse. (ISCT), Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Cerveau et vision, Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-IFR19-Institut National de la Santé et de la Recherche Médicale (INSERM), Institut des sciences du cerveau de Toulouse. (ISCT), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre Hospitalier Universitaire de Toulouse (CHU Toulouse)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre Hospitalier Universitaire de Toulouse (CHU Toulouse)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Princeton University, University of Amsterdam [Amsterdam] (UvA), University of California [Irvine] (UC Irvine), University of California (UC), BARONE, Pascal, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of California [Irvine] (UCI), University of California, and Institut cellule souche et cerveau / Stem Cell and Brain Research Institute (SBRI)

Subjects
Male, Cognitive Neuroscience, [SDV.NEU.NB]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology, Thalamus, pulvinar, deafferentation, Visual system, Lateral geniculate nucleus, Blindness, primate, Macaque, 03 medical and health sciences, Cellular and Molecular Neuroscience, 0302 clinical medicine, Extrastriate cortex, biology.animal, Cortex (anatomy), medicine, Animals, Primate, Visual Pathways, hybrid cortex, ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, Visual Cortex, Neurons, 0303 health sciences, Brain Mapping, Anophthalmia, biology, [SCCO.NEUR]Cognitive science/Neuroscience, [SCCO.NEUR] Cognitive science/Neuroscience, [SDV.NEU.NB] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology, Geniculate Bodies, medicine.disease, Macaca fascicularis, medicine.anatomical_structure, connectivity, Female, Neuroscience, 030217 neurology & neurosurgery
Abstract

There is an extensive modification of the functional organization of the brain in the congenital blind human, although there is little understanding of the structural underpinnings of these changes. The visual system of macaque has been extensively characterized both anatomically and functionally. We have taken advantage of this to examine the influence of congenital blindness in a macaque model of developmental anophthalmia. Developmental anophthalmia in macaque effectively removes the normal influence of the thalamus on cortical development leading to an induced “hybrid cortex (HC)” combining features of primary visual and extrastriate cortex. Here we show that retrograde tracers injected in early visual areas, including HC, reveal a drastic reduction of cortical projections of the reduced lateral geniculate nucleus. In addition, there is an important expansion of projections from the pulvinar complex to the HC, compared to the controls. These findings show that the functional consequences of congenital blindness need to be considered in terms of both modifications of the interareal cortical network and the ascending visual pathways.

Published
2019

2. Unique Features of Sub-Cortical Circuits in A Macaque Model of Congenital Blindness

Author

Kenneth Knoblauch, Herbert P. Killackey, Loïc Magrou, Pascale Barone, Gwylan Scheeren, Michel Berland, Colette Dehay, Nikola T. Markov, Henry Kennedy, and Pascale Giroud

Subjects
0303 health sciences, Retina, Anophthalmia, Thalamus, Visual system, Biology, medicine.disease, Lateral geniculate nucleus, Macaque, 03 medical and health sciences, 0302 clinical medicine, medicine.anatomical_structure, Extrastriate cortex, Cortex (anatomy), biology.animal, medicine, Neuroscience, 030217 neurology & neurosurgery, 030304 developmental biology
Abstract

There is extensive modification of the functional organization of the brain in the congenital blind human, although there is little understanding of the structural underpinnings of these changes. The visual system of macaque has been extensively characterized both anatomically and functionally. We have taken advantage of this to examine the influence of the congenital blindness in macaque resulting from the removal of the retina during in utero development. Developmental anophthalmia in macaque effectively removes the normal influence of the thalamus on cortical development leading to an induced hybrid cortex (HC) combining features of primary visual and extrastriate cortex. Here we show that retrograde tracers injected in early visual areas including hybrid cortex reveals a drastic reduction of cortical projections of the reduced lateral geniculate nucleus. In addition, there is an important expansion of projections from the pulvinar complex to the hybrid cortex, compared to the controls. These findings show that the functional consequences of congenital blindness need to be considered in terms of both modifications of the inter-areal cortical network and the ascending visual pathways.

Published
2019

3. A Predictive Network Model of Cerebral Cortical Connectivity Based on a Distance Rule

Author

David C. Van Essen, Kenneth Knoblauch, Camille Lamy, Mária Ercsey-Ravasz, Zoltán Toroczkai, Nikola T. Markov, and Henry Kennedy

Subjects
Computer science, Neuroscience(all), Models, Neurological, Binary number, Topology, Brain mapping, Article, 03 medical and health sciences, 0302 clinical medicine, Animals, Humans, Exponential decay, 030304 developmental biology, Network model, Cerebral Cortex, Random graph, Brain Mapping, 0303 health sciences, Quantitative Biology::Neurons and Cognition, General Neuroscience, Log-normal distribution, Macaca, Graph (abstract data type), Minification, Nerve Net, Neuroscience, 030217 neurology & neurosurgery
Abstract

SummaryRecent advances in neuroscience have engendered interest in large-scale brain networks. Using a consistent database of cortico-cortical connectivity, generated from hemisphere-wide, retrograde tracing experiments in the macaque, we analyzed interareal weights and distances to reveal an important organizational principle of brain connectivity. Using appropriate graph theoretical measures, we show that although very dense (66%), the interareal network has strong structural specificity. Connection weights exhibit a heavy-tailed lognormal distribution spanning five orders of magnitude and conform to a distance rule reflecting exponential decay with interareal separation. A single-parameter random graph model based on this rule predicts numerous features of the cortical network: (1) the existence of a network core and the distribution of cliques, (2) global and local binary properties, (3) global and local weight-based communication efficiencies modeled as network conductance, and (4) overall wire-length minimization. These findings underscore the importance of distance and weight-based heterogeneity in cortical architecture and processing.

Published
2013

4. The role of long-range connections on the specificity of the macaque interareal cortical network

Author

Pascale Giroud, Kenneth Knoblauch, Mária Ercsey-Ravasz, Nikola T. Markov, Loïc Magrou, Zoltán Toroczkai, Henry Kennedy, Pierre Misery, Ana Rita Ribeiro Gomes, David C. Van Essen, Camille Lamy, Colette Dehay, Pascal Barone, Institut cellule souche et cerveau (U846 Inserm - UCBL1), Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM), Department of Physics, University of Notre Dame [Indiana] (UND), Centre de recherche cerveau et cognition (CERCO), Institut des sciences du cerveau de Toulouse. (ISCT), Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Anatomy & Neurobiology, and University of Washington [Seattle]

Subjects
anatomy, Databases, Factual, Nerve net, Macaque, Brain mapping, 03 medical and health sciences, 0302 clinical medicine, Similarity (network science), biology.animal, medicine, Range (statistics), neocortex, Animals, 030304 developmental biology, Cerebral Cortex, Brain Mapping, 0303 health sciences, Multidisciplinary, Neocortex, biology, Biological Sciences, medicine.anatomical_structure, Geography, Cortical network, Macaca, Graph (abstract data type), [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], Nerve Net, monkey, Neuroscience, 030217 neurology & neurosurgery
Abstract

We investigated the influence of interareal distance on connectivity patterns in a database obtained from the injection of retrograde tracers in 29 areas distributed over six regions (occipital, temporal, parietal, frontal, prefrontal, and limbic). One-third of the 1,615 pathways projecting to the 29 target areas were reported only recently and deemed new-found projections (NFPs). NFPs are predominantly long-range, low-weight connections. A minimum dominating set analysis (a graph theoretic measure) shows that NFPs play a major role in globalizing input to small groups of areas. Randomization tests show that ( i ) NFPs make important contributions to the specificity of the connectivity profile of individual cortical areas, and ( ii ) NFPs share key properties with known connections at the same distance. We developed a similarity index, which shows that intraregion similarity is high, whereas the interregion similarity declines with distance. For area pairs, there is a steep decline with distance in the similarity and probability of being connected. Nevertheless, the present findings reveal an unexpected binary specificity despite the high density (66%) of the cortical graph. This specificity is made possible because connections are largely concentrated over short distances. These findings emphasize the importance of long-distance connections in the connectivity profile of an area. We demonstrate that long-distance connections are particularly prevalent for prefrontal areas, where they may play a prominent role in large-scale communication and information integration.

Published
2013

5. Cortical high-density counterstream architectures

Author

Henry Kennedy, Zoltán Toroczkai, Kenneth Knoblauch, David C. Van Essen, Mária Ercsey-Ravasz, Nikola T. Markov, Kennedy, Henry, Institut cellule souche et cerveau (U846 Inserm - UCBL1), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Recherche Agronomique (INRA), Department of Neurobiology, Yale University [New Haven], Faculty of Physics, Universitatea Babeş-Bolyai [Cluj-Napoca], Department of Anatomy & Neurobiology, University of Washington [Seattle], Department of Physics, University of Notre Dame [Indiana] (UND), Max Planck Institute for the Physics of Complex Systems (MPI-PKS), Max-Planck-Gesellschaft, This work was supported by FP6-2005 IST-1583 (H.K.), FP7-2007 ICT-216593 (H.K.), ANR-11-BSV4-501 (H.K.), LabEx CORTEX (ANR-11-LABX-0042) (H.K.), PN-II-RU-TE-2011-3-0121, FP7-PEOPLE-2011-IIF-299915 (M.E.-R.), National Institute of Mental Health grant R01 MH60974 (D.C.V.E.), Notre Dame's Interdisciplinary Center for Network Science and Applications (iCeNSA) funds, and, in part, by grant FA9550-12-1-0405 from the U.S. Air Force Office of Scientific Research and Defense Advanced Research Projects Agency (Z.T.)., Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
Nerve net, Computer science, Computation, Models, Neurological, Binary number, Topology, Article, 03 medical and health sciences, 0302 clinical medicine, Mental Processes, Feature (machine learning), medicine, Humans, [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], Representation (mathematics), 030304 developmental biology, Cerebral Cortex, 0303 health sciences, Multidisciplinary, Feed forward, Information processing, DUAL (cognitive architecture), medicine.anatomical_structure, [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], Nerve Net, 030217 neurology & neurosurgery
Abstract

International audience; Small-world networks provide an appealing description of cortical architecture owing to their capacity for integration and segregation combined with an economy of connectivity. Previous reports of low-density interareal graphs and apparent small-world properties are challenged by data that reveal high-density cortical graphs in which economy of connections is achieved by weight heterogeneity and distance-weight correlations. These properties define a model that predicts many binary and weighted features of the cortical network including a core-periphery, a typical feature of self-organizing information processing systems. Feedback and feedforward pathways between areas exhibit a dual counterstream organization, and their integration into local circuits constrains cortical computation. Here, we propose a bow-tie representation of interareal architecture derived from the hierarchical laminar weights of pathways between the high-efficiency dense core and periphery.

Published
2013

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