Neurons use action potentials to signal over long distances, as summarized in Chapter 1 by Gerstner. The all-or-none

nature of the action potential means that it codes information by its presence or absence, but not by its size or shape. In

this respect, an action potential can be considered a pulse. This is an important fact about how brains are built, but it is

equally important as a theoretical challenge to understanding the function of the brain. How do action potentials

represent sensory states? How is information contained in the firing patterns of action potentials stored and retrieved?

These are old questions that have been the focus of much research, but recent advances in experimental techniques are

opening new ways to test theories for how information is encoded and decoded by spiking neurons in neural systems

[Rieke et al., 1997]. The papers in the collection provide a window into the current state of theoretical and

computational thinking based on spikes.