Beyond Columnar Organization: Cell Type- and Target Layer-Specific Principles of Horizontal Axon Projection Patterns in Rat Vibrissal Cortex

Vertical thalamocortical afferents give rise to the elementary functional units of sensory cortex, cortical columns. Principles that underlie communication between columns remain however unknown. Here we unravel these by reconstructing in vivo-labeled neurons from all excitatory cell types in the vibrissal part of rat primary somatosensory cortex (vS1). Integrating the morphologies into an exact 3D model of vS1 revealed that the majority of intracortical (IC) axons project far beyond the borders of the principal column. We defined the corresponding innervation volume as the IC-unit. Deconstructing this structural cortical unit into its cell type-specific components, we found asymmetric projections that innervate columns of either the same whisker row or arc, and which subdivide vS1 into 2 orthogonal [supra-]granular and infragranular strata. We show that such organization could be most effective for encoding multi whisker inputs. Communication between columns is thus organized by multiple highly specific horizontal projection patterns, rendering IC-units as the primary structural entities for processing complex sensory stimuli.

[1]  W. Nauta,et al.  Silver impregnation of degenerating axons in the central nervous system: a modified technic. , 1954, Stain technology.

[2]  V. Mountcastle.  Modality and topographic properties of single neurons of cat's somatic sensory cortex. , 1957, Journal of neurophysiology.

[3]  D. Hubel,et al.  Receptive fields of single neurones in the cat's striate cortex , 1959, The Journal of physiology.

[4]  V. Braitenberg,et al.  A note on myeloarchitectonics , 1962, The Journal of comparative neurology.

[5]  T. Woolsey,et al.  The structural organization of layer IV in the somatosensory region (SI) of mouse cerebral cortex. The description of a cortical field composed of discrete cytoarchitectonic units. , 1970, Brain research.

[6]  T. Woolsey,et al.  The structural organization of layer IV in the somatosensory region (S I) of mouse cerebral cortex , 1970 .

[7]  T. Powell,et al.  The intrinsic, association and commissural connections of area 17 on the visual cortex. , 1975, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[8]  S. Wise,et al.  Cells of origin and terminal distribution of descending projections of the rat somatic sensory cortex , 1977, The Journal of comparative neurology.

[9]  T. Wiesel,et al.  Morphology and intracortical projections of functionally characterised neurones in the cat visual cortex , 1979, Nature.

[10]  M. Wong-Riley.  Changes in the visual system of monocularly sutured or enucleated cats demonstrable with cytochrome oxidase histochemistry , 1979, Brain Research.

[11]  A. L. Humphrey,et al.  Anatomical banding of intrinsic connections in striate cortex of tree shrews (Tupaia glis) , 1982, The Journal of comparative neurology.

[12]  J. Lund,et al.  Widespread periodic intrinsic connections in the tree shrew visual cortex. , 1982, Science.

[13]  T. Wiesel,et al.  Clustered intrinsic connections in cat visual cortex , 1983, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[14]  K. Horikawa,et al.  A versatile means of intracellular labeling: injection of biocytin and its detection with avidin conjugates , 1988, Journal of Neuroscience Methods.

[15]  T A Woolsey,et al.  Local intra‐ and interlaminar connections in mouse barrel cortex , 1990, The Journal of comparative neurology.

[16]  E. G. Jones,et al.  Relationship of intrinsic connections to forelimb movement representations in monkey motor cortex: a correlative anatomic and physiological study. , 1991, Journal of neurophysiology.

[17]  A Keller,et al.  Intrinsic synaptic organization of the motor cortex. , 1993, Cerebral cortex.

[18]  J. B. Levitt,et al.  Topography of pyramidal neuron intrinsic connections in macaque monkey prefrontal cortex (areas 9 and 46) , 1993, The Journal of comparative neurology.

[19]  Asaf Keller,et al.  Synaptic relationships involving local axon collaterals of pyramidal neurons in the cat motor cortex , 1993, The Journal of comparative neurology.

[20]  A Keller,et al.  Specific patterns of intrinsic connections between representation zones in the rat motor cortex. , 1994, Cerebral cortex.

[21]  P. Goldman-Rakic.  Cellular basis of working memory , 1995, Neuron.

[22]  D. Pinault,et al.  A novel single-cell staining procedure performed in vivo under electrophysiological control: morpho-functional features of juxtacellularly labeled thalamic cells and other central neurons with biocytin or Neurobiotin , 1996, Journal of Neuroscience Methods.

[23]  M. Deschenes,et al.  Intracortical Axonal Projections of Lamina VI Cells of the Primary Somatosensory Cortex in the Rat: A Single-Cell Labeling Study , 1997, The Journal of Neuroscience.

[24]  D. Fitzpatrick,et al.  Orientation Selectivity and the Arrangement of Horizontal Connections in Tree Shrew Striate Cortex , 1997, The Journal of Neuroscience.

[25]  E. Miller,et al.  Memory fields of neurons in the primate prefrontal cortex. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[26]  J. Lübke,et al.  Reliable synaptic connections between pairs of excitatory layer 4 neurones within a single ‘barrel’ of developing rat somatosensory cortex , 1999, The Journal of physiology.

[27]  Hans-Peter Kriegel,et al.  OPTICS: ordering points to identify the clustering structure , 1999, SIGMOD '99.

[28]  J. Lübke,et al.  Columnar Organization of Dendrites and Axons of Single and Synaptically Coupled Excitatory Spiny Neurons in Layer 4 of the Rat Barrel Cortex , 2000, The Journal of Neuroscience.

[29]  Bert Sakmann,et al.  Whisker maps of neuronal subclasses of the rat ventral posterior medial thalamus, identified by whole‐cell voltage recording and morphological reconstruction , 2002, The Journal of physiology.

[30]  B. Sakmann,et al.  ‐Dynamic representation of whisker deflection by synaptic potentials in spiny stellate and pyramidal cells in the barrels and septa of layer 4 rat somatosensory cortex , 2002, The Journal of physiology.

[31]  B. Sakmann,et al.  Dynamic Receptive Fields of Reconstructed Pyramidal Cells in Layers 3 and 2 of Rat Somatosensory Barrel Cortex , 2003, The Journal of physiology.

[32]  A. Grinvald,et al.  Spatiotemporal Dynamics of Sensory Responses in Layer 2/3 of Rat Barrel Cortex Measured In Vivo by Voltage-Sensitive Dye Imaging Combined with Whole-Cell Voltage Recordings and Neuron Reconstructions , 2003, The Journal of Neuroscience.

[33]  R. Douglas,et al.  Neuronal circuits of the neocortex. , 2004, Annual review of neuroscience.

[34]  O. Creutzfeldt,et al.  The distribution of degenerating axons after small lesions in the intact and isolated visual cortex of the cat , 1977, Experimental Brain Research.

[35]  Bert Sakmann,et al.  Sub‐ and suprathreshold receptive field properties of pyramidal neurones in layers 5A and 5B of rat somatosensory barrel cortex , 2004, The Journal of physiology.

[36]  R. Douglas,et al.  A Quantitative Map of the Circuit of Cat Primary Visual Cortex , 2004, The Journal of Neuroscience.

[37]  Karl Zilles,et al.  Functional diversity of layer IV spiny neurons in rat somatosensory cortex: quantitative morphology of electrophysiologically characterized and biocytin labeled cells. , 2004, Cerebral cortex.

[38]  Randy M Bruno,et al.  The Role of Thalamic Inputs in Surround Receptive Fields of Barrel Neurons , 2005, The Journal of Neuroscience.

[39]  Vincent Jacob,et al.  Spatiotemporal characteristics of neuronal sensory integration in the barrel cortex of the rat. , 2005, Journal of neurophysiology.

[40]  J. Lübke,et al.  Efficacy and connectivity of intracolumnar pairs of layer 2/3 pyramidal cells in the barrel cortex of juvenile rats , 2006, The Journal of physiology.

[41]  R Kötter,et al.  Morphology, electrophysiology and functional input connectivity of pyramidal neurons characterizes a genuine layer va in the primary somatosensory cortex. , 2006, Cerebral cortex.

[42]  H. Markram.  The Blue Brain Project , 2006, Nature Reviews Neuroscience.

[43]  Randy M Bruno,et al.  Transmitted light brightfield mosaic microscopy for three-dimensional tracing of single neuron morphology. , 2007, Journal of biomedical optics.

[44]  Cpj de Kock,et al.  Layer‐ and cell‐type‐specific suprathreshold stimulus representation in rat primary somatosensory cortex , 2007, The Journal of physiology.

[45]  Rafael Yuste,et al.  Two-photon photostimulation and imaging of neural circuits , 2007, Nature Methods.

[46]  Bert Sakmann,et al.  Sensory integration across space and in time for decision making in the somatosensory system of rodents , 2007, Proceedings of the National Academy of Sciences.

[47]  Randy M Bruno,et al.  Subcolumnar dendritic and axonal organization of spiny stellate and star pyramid neurons within a barrel in rat somatosensory cortex. , 2008, Cerebral cortex.

[48]  O. Ohana,et al.  Inter- and intralaminar subcircuits of excitatory and inhibitory neurons in layer 6a of the rat barrel cortex. , 2008, Journal of neurophysiology.

[49]  C. Petersen,et al.  The Excitatory Neuronal Network of the C2 Barrel Column in Mouse Primary Somatosensory Cortex , 2009, Neuron.

[50]  K. Svoboda,et al.  The subcellular organization of neocortical excitatory connections , 2009, Nature.

[51]  Damian J. Wallace,et al.  Sensory Experience Alters Specific Branches of Individual Corticocortical Axons during Development , 2009, The Journal of Neuroscience.

[52]  S. Hestrin,et al.  Intracortical circuits of pyramidal neurons reflect their long-range axonal targets , 2009, Nature.

[53]  Nathalie L Rochefort,et al.  Dendritic organization of sensory input to cortical neurons in vivo , 2010, Nature.

[54]  B. Sakmann,et al.  Dimensions of a Projection Column and Architecture of VPM and POm Axons in Rat Vibrissal Cortex , 2010, Cerebral cortex.

[55]  H. S. Meyer,et al.  Number and Laminar Distribution of Neurons in a Thalamocortical Projection Column of Rat Vibrissal Cortex , 2010, Cerebral cortex.

[56]  Karel Svoboda,et al.  The Past, Present, and Future of Single Neuron Reconstruction , 2011, Neuroinformatics.

[57]  B. Sakmann,et al.  Three-dimensional axon morphologies of individual layer 5 neurons indicate cell type-specific intracortical pathways for whisker motion and touch , 2011, Proceedings of the National Academy of Sciences.

[58]  Bert Sakmann,et al.  Dendritic coding of multiple sensory inputs in single cortical neurons in vivo , 2011, Proceedings of the National Academy of Sciences.

[59]  Moritz Helmstaedter,et al.  3D Reconstruction and Standardization of the Rat Vibrissal Cortex for Precise Registration of Single Neuron Morphology , 2012, PLoS Comput. Biol..

[60]  H. S. Meyer,et al.  Cell Type–Specific Three-Dimensional Structure of Thalamocortical Circuits in a Column of Rat Vibrissal Cortex , 2011, Cerebral cortex.

[61]  E. Welker,et al.  Intracortical connectivity of layer VI pyramidal neurons in the somatosensory cortex of normal and barrelless mice , 2012, The European journal of neuroscience.

[62]  Israel Nelken,et al.  Sound‐evoked network calcium transients in mouse auditory cortex in vivo , 2012, The Journal of physiology.

[63]  H. S. Meyer,et al.  Cellular organization of cortical barrel columns is whisker-specific , 2013, Proceedings of the National Academy of Sciences.

[64]  Sylvain Crochet,et al.  Synaptic Computation and Sensory Processing in Neocortical Layer 2/3 , 2013, Neuron.

[65]  F. Helmchen,et al.  Barrel cortex function , 2013, Progress in Neurobiology.

[66]  Hans-Christian Hege,et al.  The Filament Editor: An Interactive Software Environment for Visualization, Proof-Editing and Analysis of 3D Neuron Morphology , 2013, Neuroinformatics.

[67]  Christine M Constantinople,et al.  Deep Cortical Layers Are Activated Directly by Thalamus , 2013, Science.

[68]  Ian R. Wickersham,et al.  The Stimulus Selectivity and Connectivity of Layer Six Principal Cells Reveals Cortical Microcircuits Underlying Visual Processing , 2014, Neuron.

[69]  Hans-Christian Hege,et al.  Generation of dense statistical connectomes from sparse morphological data , 2014, Front. Neuroanat..

[70]  Liam Paninski,et al.  Spatiotemporal receptive fields of barrel cortex revealed by reverse correlation of synaptic input , 2014, Nature Neuroscience.

[71]  Rajeevan T Narayanan,et al.  Juxtasomal biocytin labeling to study the structure-function relationship of individual cortical neurons. , 2014, Journal of visualized experiments : JoVE.