A gradual depth-dependent change in connectivity features of supragranular pyramidal cells in rat barrel cortex

Brain Struct Funct. 2015;220(3):1317-37. doi: 10.1007/s00429-014-0726-8. Epub 2014 Feb 26.


Recent experimental evidence suggests a finer genetic, structural and functional subdivision of the layers which form a cortical column. The classical layer II/III (LII/III) of rodent neocortex integrates ascending sensory information with contextual cortical information for behavioral read-out. We systematically investigated to which extent regular-spiking supragranular pyramidal neurons, located at different depths within the cortex, show different input-output connectivity patterns. Combining glutamate uncaging with whole-cell recordings and biocytin filling, we revealed a novel cellular organization of LII/III: (1) "Lower LII/III" pyramidal cells receive a very strong excitatory input from lemniscal LIV and much fewer inputs from paralemniscal LVa. They project to all layers of the home column, including a feedback projection to LIV, whereas transcolumnar projections are relatively sparse. (2) "Upper LII/III" pyramidal cells also receive their strongest input from LIV, but in addition, a very strong and dense excitatory input from LVa. They project extensively to LII/III as well as LVa and Vb of their home and neighboring columns. (3) "Middle LII/III" pyramidal cell shows an intermediate connectivity phenotype that stands in many ways in between the features described for lower versus upper LII/III. "Lower LII/III" intracolumnarly segregates and transcolumnarly integrates lemniscal information, whereas "upper LII/III" seems to integrate lemniscal with paralemniscal information. This suggests a fine-grained functional subdivision of the supragranular compartment containing multiple circuits without any obvious cytoarchitectonic, other structural or functional correlate of a laminar border in rodent barrel cortex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Animals
  • Electrophysiology / methods
  • Glutamic Acid / pharmacology
  • In Vitro Techniques
  • Neural Pathways / drug effects
  • Neural Pathways / physiology*
  • Patch-Clamp Techniques / methods
  • Pyramidal Cells / cytology
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / physiology*
  • Rats
  • Somatosensory Cortex / cytology*
  • Somatosensory Cortex / drug effects
  • Somatosensory Cortex / physiology*


  • Glutamic Acid