Forward Dendritic Spikes: A Mechanism for Parallel Processing in Dendritic Subunits and Shifting Output Codes

Channels In Dendrites: A Conceptual Revolution

Based on modeling studies, some authors, suggested that the overall firing pattern is somehow engraved in the architecture of the dendritic tree (Mainen et al., 1995). Indeed, some architectonic dendritic prototypes have been preserved in specific brain nuclei spanning long periods of brain evolution. Although this may be indicative of a common integrative function being preserved to carry out a specific task, the large number of exceptions clearly argue against this hypothesis. Certainly, the physical structure of the dendritic arbors has a notable influence in the processing of inputs, and even some computational capabilities arise from it (see Segev and London, 1999). Nevertheless, most dendrites are active neuron elements, not mere passive cables. The number and variety of ion channels in their membranes modulate synaptic currents with a strength and complexity largely overcoming that of the cable structure. These “modulatory” dendritic currents have the same voltage-dependent nature as those in the soma and axon, and have been called intrinsic currents to differentiate them from the synaptic currents that co-activate and co-localize with them.