Dense, unspecific connectivity of neocortical parvalbumin-positive interneurons: a canonical microcircuit for inhibition?

J Neurosci. 2011 Sep 14;31(37):13260-71. doi: 10.1523/JNEUROSCI.3131-11.2011.


GABAergic interneurons play a major role in the function of the mammalian neocortex, but their circuit connectivity is still poorly understood. We used two-photon RuBi-Glutamate uncaging to optically map how the largest population of cortical interneurons, the parvalbumin-positive cells (PV+), are connected to pyramidal cells (PCs) in mouse neocortex. We found locally dense connectivity from PV+ interneurons onto PCs across cortical areas and layers. In many experiments, all nearby PV+ cells were connected to every local PC sampled. In agreement with this, we found no evidence for connection specificity, as PV+ interneurons contacted PC pairs similarly regardless of whether they were synaptically connected or not. We conclude that the microcircuit architecture for PV+ interneurons, and probably neocortical inhibition in general, is an unspecific, densely homogenous matrix covering all nearby pyramidal cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Mapping / methods
  • Female
  • In Vitro Techniques
  • Interneurons / physiology*
  • Male
  • Mice
  • Mice, Transgenic
  • Microscopy, Confocal / methods
  • Neocortex / anatomy & histology
  • Neocortex / physiology*
  • Neural Inhibition / physiology*
  • Neural Pathways / anatomy & histology*
  • Neural Pathways / physiology*
  • Parvalbumins / genetics
  • Patch-Clamp Techniques / methods
  • Pyramidal Cells / physiology


  • Parvalbumins