title: Physiology and Impact of Horizontal Connections in Rat Neocortex.
abstract: Cortical information processing at the cellular level has predominantly been studied in local networks, which are dominated by strong vertical connectivity between layers. However, recent studies suggest that the bulk of axons targeting pyramidal neurons most likely originate from outside this local range, emphasizing the importance of horizontal connections. We mapped a subset of these connections to L5B pyramidal neurons in rat somatosensory cortex with photostimulation, identifying intact projections up to a lateral distance of 2 mm. Our estimates of the spatial distribution of cells presynaptic to L5B pyramids support the idea that the majority is located outside the local volume. The synaptic physiology of horizontal connections does not differ markedly from that of local connections, whereas the layer and cell-type-dependent pattern of innervation does. Apart from L2/3, L6A provides a strong source of horizontal connections. Implementing our data into a spiking neuronal network model shows that more horizontal connections promote robust asynchronous ongoing activity states and reduce noise correlations in stimulus-induced activity.
authors.affiliation: Bernstein Center Freiburg, Freiburg 79104, Germany Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Schnepel
authors.affiliation: Bernstein Center Freiburg, Freiburg 79104, Germany Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.
authors.forename: Arvind
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Bernstein Center Freiburg, Freiburg 79104, Germany Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.
authors.forename: Mihael
authors.initials: M
authors.lastname: Zohar
authors.affiliation: Bernstein Center Freiburg, Freiburg 79104, Germany Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.
authors.forename: Ad
authors.initials: A
authors.lastname: Aertsen
authors.affiliation: Bernstein Center Freiburg, Freiburg 79104, Germany Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Boucsein
mesh_terms: D000200:Action Potentials; D000818:Animals; D019706:Excitatory Postsynaptic Potentials; D008959:Models, Neurological; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D016571:Neural Networks, Computer; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D013003:Somatosensory Cortex / Q000166:cytology* / Q000502:physiology*; D013569:Synapses / Q000502:physiology
keywords: cortical network; horizontal connections; laser uncaging; noise correlation; pyramidal neuron