Laminar and columnar organization of ascending excitatory projections to layer 2/3 pyramidal neurons in rat barrel cortex

Gordon M G Shepherd, Karel Svoboda*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

176 Scopus citations


Excitatory synaptic projections to layer 2/3 (L2/3) pyramidal neurons in brain slices from the rat barrel cortex were measured using quantitative laser-scanning photostimulation (LSPS) mapping. In the barrel cortex, cytoarchitectonic "barrels" and "septa" in L4 define a stereotypical array of landmarks, allowing alignment and averaging of LSPS maps from multiple cells in different slices. We distinguished inputs to L2 and L3 neurons above barrels and septa. Average input maps revealed that barrel-related ascending projections (L4→2/3barrel) interdigitated with a novel septum-related projection (L5A→2septum). We also explored the functional organization of these projections by comparing the input maps of multiple cells in individual slices. L2/3 cells sharing the same barrel-related column showed strong correlations in their input maps, independent of their precise locations within the column; otherwise, correlations fell rapidly as a function of intersomatic separation. Our data indicate that barrel-related and septum-related columns are associated with distinct functional circuits. These projections are likely to mediate parallel processing of somatosensory signals within the barrel cortex, with L4→2/3barrel and L5A→2 septum representing the intracortical continuations of, respectively, the subcortical lemniscal and paralemniscal systems conveying somatosensory information to the barrel cortex.

Original languageEnglish (US)
Pages (from-to)5670-5679
Number of pages10
JournalJournal of Neuroscience
Issue number24
StatePublished - Jun 15 2005


  • Barrel
  • Connectivity
  • Cortex
  • Glutamate uncaging
  • Microcircuit
  • Paralemniscal
  • Photostimulation
  • Septum
  • Somatosensory

ASJC Scopus subject areas

  • General Neuroscience


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