Emerging Principles Governing the Operation of Neural Networks

ical, and computational techniques have provided the tools to begin uncovering concepts underlying neural network function. This review is a summary of insights into the organization and operation of neural circuits acquired through application of these techniques to invertebrate and vertebrate systems. This review is not a survey of the vast variety of known neural networks but rather concentrates on emerging concepts applicable to net­ works in general. The first section provides a brief historical perspective. The second and third sections summarize two emerging concepts about the operation and modulation of neural circuits. The first concept is that the operation of a neural network depends upon interactions among mul­ tiple nonlinear processes at the cellular, synaptic, and network levels. The second concept is that modulation of these underlying processes can alter network operation. The final section suggests potentially profitable research directions for the future.