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- Title
Morphometric Analysis of the Columnar Innervation Domain of Neurons Connecting Layer 4 and Layer 2/3 of Juvenile Rat Barrel Cortex.
- Authors
Lübke, Joachim; Roth, Arnd; Feldmeyer, Dirk; Sakmann, Bert
- Abstract
We have investigated the dendritic and axonal morphology of connected pairs of L4 spiny neurons and L2/3 pyramidal cells in rat barrel cortex. The ‘projection’ field of the axons of L4 spiny neurons in layers 2/3, 4 and 5 has a width of 400–500 μm thereby defining an anatomical barrel-column. In layer 2/3, the averaged axonal ‘projection’ field of L4 spiny neurons together with the dendritic ‘receptive’ field of the connected L2/3 pyramidal cells form a mostly column-restricted anatomical L4-to-L2/3 ‘innervation domain’ that extends 300–400 μm and includes mostly basal dendrites. In the L4-to-L2/3 innervation domain a single L4 spiny neuron contacts ~300–400 pyramidal cells while in the L4-to-L4 innervation domain it contacts ~200 other L4 spiny neurons. Similarly ~300–400 L4 spiny neurons converge onto a single pyramidal cell and ~200 L4 spiny neurons innervate another L4 spiny neuron. The L2/3 pyramidal cell axon has a vertical projection field spanning all cortical layers, and a long-range horizontal field in layers 2/3 (width 1100–1200 μm) and 5 (700–800 μm) projecting across column borders. The results suggest that the flow of excitation within a barrel-column is determined by the largely columnar confinement of the L4-to-L4 and L4-to-L2/3 innervation domains. A whisker deflection activates ~140 L4 spiny neurons that will generate EPSPs in most barrel-related L2/3 pyramidal cells of a principal whisker column. The translaminar synaptic transmission to layer 2/3 and the axonal projection fields of L2/3 pyramidal cells are the major determinants of the dynamic, multi-columnar map in which a single whisker deflection is represented in the cortex.
- Publication
Cerebral Cortex, 2003, Vol 13, Issue 10, p1051
- ISSN
1047-3211
- Publication type
Article
- DOI
10.1093/cercor/13.10.1051