Any live dendrite contains constitutive parts, such as the artificial elements used in Chapters 7 and 8 to demonstrate the biophysical laws that rule the proximal-todistal and path-to-path electrical relationships. In fact, the live dendrite is made of similar elements and is ruled by the same laws. However, any piece of dendrite observed under a microscope in an histological preparation displays a much more complex shape than artificial elements. It appears tortuous, irregular, often nodular with branching points and daughter branches of different lengths and diameters. These idiosyncratic attributes are totally unpredictable, making dendrites unique.

In this chapter, as we tackle much more complex live objects, we consider first natural dendritic structures of moderate complexity: individual dendrites extracted from a whole arborization. We study electrical structures of natural dendrites in the same way as we did in the previous chapters dealing with simplified artificially built structures. We look for geometry-related features in the electrical structures in relation to structural heterogeneities and branchings in their natural occurrence. As the recognizable geometry-related features of electric structures are found for individual dendrites, they will be used as navigation tools in electrical structures of complex arborizations of different neuron types described in Chapter 11.

Geometry of an example dendrite

Here we show an example of a systematic study performed on one individual dendrite extracted from the reconstructed arborization of an abducens motoneuron of the rat (cell M5 in Figure 9.5). The location of the selected dendrite in the 3D space surrounding the soma is shown in Figure 10.1, A (Korogod et al., 1998).