Structural plasticity at the axodendritic interface: some functional implications

Mel, B. W. (2003). In: Van Ooyen, A., ed. Modeling Neural Development. Cambridge, MA: MIT Press, pp. 273-290.

Abstract

Models of development and learning have often focused on the establishment or modification of synaptic connections between classical 'point' neurons. However, the notion that a neuron's internal state can be characterized by a single value is challenged by recent evidence indicating that dendritic trees can provide a significant degree of internal compartmentalization of their electrical signals. Recent experiments have shown, for example, that synaptically evoked dendritic spikes mediated by NMDA, Na, and Ca channels can remain confined to individual thin dendrites or even small portions of dendrites, suggesting that nonlinear thresholding of synaptic inputs could take place on a compartment-by-compartment basis.

The potential importance of neuronal compartmentalization is magnified when coupled with evidence for continuous structural remodeling at the interface between axons and dendrites, which may continue throughout life. This combination of effects -- subunitized neurons and fine-grained structural plasticity -- raises the possibility that activity-dependent mechanisms may control the targeting of synaptic contacts, not just onto neurons as undifferentiated wholes, but onto specific dendritic subregions. We show how this shift in model granularity fundamentally alters the way new information is incorporated into neural tissue, and leads to much higher storage capacities than have been conventionally assumed.