Thus, the study of axonal and dendritic morphology plays a prominent role in the continuous investigation

of neuronal activity and function. Yet, even some basic questions remain outstanding. For example, one of the most studied neuron types, cortical pyramidal cells, are characterized by morphologically distinct basal and apical dendrites, which receive distinctly organized synaptic inputs from different afferents and brain regions, but the functional implication of such a design is still not fully understood (Spruston, 2008). Computational models have shown that dendritic geometry can be responsible for producing the entire spectrum of firing patterns displayed across different cortical neuron types (Mainen and Sejnowski, 1996) and within a single class of electrophysiologically heterogeneous hippocampal neurons (Krichmar et al., 2002). The morphological development of these arbors influences synaptic organization Epigenetic inhibitor ic50 and neural activity, which leaves a critical open question about the relationship between structure and function during growth. Here, we briefly review the earlier history of the scientific characterization of axonal and dendritic morphology, leading to the current digital era (for a more thorough account, see Senft, 2011). We then outline how the establishment of a PLX4032 manufacturer standard digital format for reconstructions

of neuronal arbors catalyzed the emergence of a thriving research community that spans subdisciplines, techniques,

and scientific questions. In the late 19th and early 20th centuries, Ramón y Cajal adopted Golgi’s staining technique to produce a revolutionary series of drawings of dendritic and (unmyelinated) axonal morphology that remain to this day absolutely remarkable for both their sheer amount and level of detail. This collection provided the foundation to approach the investigation of the structure-function relationship in nervous systems. The fundamental principles recognized by Cajal included the directional flow of impulses between neurons, the diversity of microcircuit motifs, and the specificity of network connectivity. Cajal’s work also established the intertwined all relationship of three key processes in the characterization of neuronal morphology: histological preparation, light microscopic visualization, and accurate tracing. The spectacular morphological exuberance of axons and dendrites revealed by the Golgi stain could only be properly captured by faithful tracing of the arbors and their circuits. It also became apparent that neuronal trees, due to their enormous span relative to the caliber of individual branches, could not simply be reproduced (e.g., photographically) but needed to be reconstructed from numerous focal depths and fields of view. Subsequently, interest in cellular neuroanatomy has seen its ups and downs, reflecting stages of advances and stagnation.