Regenerative dendritic spikes and synaptic plasticity

During the last decade, our vision of the neuronal dendritic tree has changed from a simple input device conducting afferent input as a passive cable to the cell soma to a series of independent and actively operating processing units. Different voltage- and ligand-gated ion channels located in the dendritic tree not only participate in processing afferent inputs but also enable the dendritic tree to initiate regenerative spikes, traditionally considered to be exclusively restricted to axonal structures. Recent results suggest that these local dendritic spikes may act as a means to initiate long-term synaptic plasticity. Different from Hebbian synaptic plasticity this type of induction does not need axonal action potential firing and backpropagation into the dendrite. This new proximity learning rule, first postulated by neural network theorists, may have large significance for the information processing in the brain.