title: A gradual depth-dependent change in connectivity features of supragranular pyramidal cells in rat barrel cortex.
abstract: 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.
authors.affiliation: Institute for Neuroanatomy, University Medicine Göttingen, Kreuzbergring 36, 37075, Göttingen, Germany, jochen.staiger@med.uni-goettingen.de.
authors.forename: Jochen F
authors.initials: JF
authors.lastname: Staiger
authors.forename: Ingo
authors.initials: I
authors.lastname: Bojak
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Miceli
authors.forename: Dirk
authors.initials: D
authors.lastname: Schubert
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004594:Electrophysiology / Q000379:methods; D018698:Glutamic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D017966:Pyramidal Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013003:Somatosensory Cortex / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*
chemical_list: D018698:Glutamic Acid