Summary
In frontal and tangential paraffin sections through the sensory-motor cortex of the rabbit, vertical bundles of dendrites have been found. Each bundle consists of several apical dendrites of layer V pyramids and extends through layer IV into layer III/II where the dendrites begin to ramify. Electron microscopy reveals that within the bundle some of the dendrites approach each other so closely as to be separated by the extracellular space only. A vertical bundling of dendrites has, also been found in various regions of the sensory-motor cortex of the cat. — The hypothesis is put forward that the vertical bundles of dendrites are the morphological substrate of the vertical functional units deduced from electrophysiological observations.
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