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Front. Neuroanat. | doi: 10.3389/fnana.2018.00033

Diverse long-range axonal projections of excitatory layer 2/3 neurons in mouse barrel cortex

  • 1Laboratory of Sensory Processing, Brain Mind Inst., Ecole Polytechnique Fédérale de Lausanne, Switzerland
  • 2Department of Neuroscience II, Nagoya University, Japan
  • 3Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, United States

Excitatory projection neurons of the neocortex are thought to play important roles in perceptual and cognitive functions of the brain by directly connecting diverse cortical and subcortical areas. However, many aspects of the anatomical organization of these inter-areal connections are unknown. Here, we studied long-range axonal projections of excitatory layer 2/3 neurons with cell bodies located in mouse primary somatosensory barrel cortex (wS1). As a population, these neurons densely projected to secondary whisker somatosensory cortex (wS2) and primary/secondary whisker motor cortex (wM1/2), with additional axon in the dysgranular zone surrounding the barrel field, perirhinal temporal association cortex and striatum. In three-dimensional reconstructions of 6 individual wS2-projecting neurons and 9 individual wM1/2-projecting neurons, we found that both classes of neurons had extensive local axon in layers 2/3 and 5 of wS1. Neurons projecting to wS2 did not send axon to wM1/2, whereas a small subset of wM1/2-projecting neurons had relatively weak projections to wS2. A small fraction of projection neurons solely targeted wS2 or wM1/2. However, axon collaterals from wS2-projecting and wM1/2-projecting neurons were typically also found in subsets of various additional areas, including the dysgranular zone, perirhinal temporal association cortex and striatum. Our data suggest extensive diversity in the axonal targets selected by individual nearby cortical long-range projection neurons with somata located in layer 2/3 of wS1.

Keywords: Neocortex, barrel cortex, projection neurons, axonal structure, layer 2/3 pyramidal neuron

Received: 28 Feb 2018; Accepted: 16 Apr 2018.

Edited by:

Pablo Blinder, Tel Aviv University, Israel

Reviewed by:

Joachim H. Lübke, Forschungszentrum Jülich, Germany
Christiaan P. De Kock, VU University Amsterdam, Netherlands  

Copyright: © 2018 Yamashita, Vavladeli, Pala, Galan, Crochet, Petersen and Petersen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Carl Petersen, Ecole Polytechnique Fédérale de Lausanne, Laboratory of Sensory Processing, Brain Mind Inst., Lausanne, CH-1015, Switzerland, carl.petersen@epfl.ch