Top-down laminar organization of the excitatory network in motor cortex

Nat Neurosci. 2008 Mar;11(3):360-6. doi: 10.1038/nn2049. Epub 2008 Feb 3.


Cortical layering is a hallmark of the mammalian neocortex and a major determinant of local synaptic circuit organization in sensory systems. In motor cortex, the laminar organization of cortical circuits has not been resolved, although their input-output operations are crucial for motor control. Here, we developed a general approach for estimating layer-specific connectivity in cortical circuits and applied it to mouse motor cortex. From these data we computed a laminar presynaptic --> postsynaptic connectivity matrix, W(post,pre), revealing a complement of stereotypic pathways dominated by layer 2 outflow to deeper layers. Network modeling predicted, and experiments with disinhibited slices confirmed, that stimuli targeting upper, but not lower, cortical layers effectively evoked network-wide events. Thus, in motor cortex, descending excitation from a preamplifier-like network of upper-layer neurons drives output neurons in lower layers. Our analysis provides a quantitative wiring-diagram framework for further investigation of the excitatory networks mediating cortical mechanisms of motor control.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Animals
  • Brain Mapping
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Glutamic Acid / metabolism
  • Glutamic Acid / pharmacology
  • Mice
  • Motor Cortex / anatomy & histology
  • Motor Cortex / drug effects
  • Motor Cortex / physiology*
  • Nerve Net / anatomy & histology
  • Nerve Net / drug effects
  • Nerve Net / physiology*
  • Neural Networks, Computer
  • Neural Pathways / anatomy & histology
  • Neural Pathways / drug effects
  • Neural Pathways / physiology
  • Neurons / drug effects
  • Neurons / physiology*
  • Organ Culture Techniques
  • Photic Stimulation
  • Photochemistry
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology*


  • Glutamic Acid