PT  - JOURNAL ARTICLE
AU  - Joachim Lübke
AU  - Veronica Egger
AU  - Bert Sakmann
AU  - Dirk Feldmeyer
TI  - Columnar Organization of Dendrites and Axons of Single and Synaptically Coupled Excitatory Spiny Neurons in Layer 4 of the Rat Barrel Cortex
AID  - 10.1523/JNEUROSCI.20-14-05300.2000
DP  - 2000 Jul 15
TA  - The Journal of Neuroscience
PG  - 5300--5311
VI  - 20
IP  - 14
4099  - http://www.jneurosci.org/content/20/14/5300.short
4100  - http://www.jneurosci.org/content/20/14/5300.full
SO  - J. Neurosci.2000 Jul 15; 20
AB  - Cortical columns are the functional units of the neocortex that are particularly prominent in the “barrel” field of the somatosensory cortex. Here we describe the morphology of two classes of synaptically coupled excitatory neurons in layer 4 of the barrel cortex, spiny stellate, and star pyramidal cells, respectively. Within a single barrel, their somata tend to be organized in clusters. The dendritic arbors are largely confined to layer 4, except for the distal part of the apical dendrite of star pyramidal neurons that extends into layer 2/3. In contrast, the axon of both types of neurons spans the cortex from layer 1 to layer 6. The most prominent axonal projections are those to layers 4 and 2/3 where they are largely restricted to a single cortical column. In layers 5 and 6, a small fraction of axon collaterals projects also across cortical columns. Consistent with the dense axonal projection to layers 4 and 2/3, the total number and density of boutons per unit axonal length was also highest there. Electron microscopy combined with GABA postimmunogold labeling revealed that most (>90%) of the synaptic contacts were established on dendritic spines and shafts of excitatory neurons in layers 4 and 2/3.The largely columnar organization of dendrites and axons of both cell types, combined with the preferential and dense projections within cortical layers 4 and 2/3, suggests that spiny stellate and star pyramidal neurons of layer 4 serve to amplify thalamic input and relay excitation vertically within a single cortical column.