A theoretical view of the neuron as a plastic input-output device

Wilfrid Rall developed the theoretical foundations for understanding dendritic function almost fifty years ago. Since then his theory has been intensely employed and extended in order to explore the biophysical principles that link together the structure, physiology, and function of dendrites. This chapter highlights some of the main insights that were gained from this theory, specifically emphasizing the relationship between the local activation of a synapse on a dendrite and the overall synaptic activity in the neuron. It discusses the contribution of a single synapse out of numerous active synapses to a neuron's firing pattern and describes a new measure to quantify the efficacy of a single synapse, using tools borrowed from information theory. It reviews the local and global aspects of the electrical activity in dendrites, and explores the effect of local versus global mechanisms of a specific form of synaptic plasticity, homeostatic synaptic plasticity.