Fig. 1.

Confocal imaging and 3D reconstructions of pairs and triplets of layer V pyramidal neurons. (A) Flattened representation from 3D image stacks of a pair of pyramidal neurons in layer V, as acquired by confocal microscopy. The entire span of the neurons is captured, allowing for a detailed investigation of all apposition points between axons and dendrites. (B) The high resolution of confocal imaging allowed for unambiguous tracing of axons and dendrites to create detailed 3D reconstructions. The higher neuron is colored blue for soma and dendrites and red for the axon. The lower neuron is colored green for soma and dendrites and black for the axon. (C) Geometrical connectivity between pyramidal neurons of layer V can be predicted from their characteristic morphology. We assumed a setting of two layer V pyramidal neurons with any spatial separation between their somata. The contour plot shows the expected number of touch sites as a function of the relative somatic location of the two neurons when one of them is located at the center. The plot was calculated from the neuronal morphologies obtained from the 3D reconstructions (18) and corrected for neuropil volume.