Even the simplest neural networks can give rise to multiple combinations of firing patterns (Abeles, 1991). Whether one or several of the possible combinations of firing patterns are meaningful can be determined only by a reader-classifier mechanism. If multiple combinations elicit the same output in one reader, they are interpreted as identical from the point of view of the reader. Another reader mechanism may respond to another set of combination of firing patterns. A simple and ubiquitous example of a reader mechanism in the brain is the integration of presynaptic spikes by neurons, constrained by their membrane time constant τ.4 A group of upstream neurons, whose spike discharges occur within the window of the membrane time constant of the reader-integrator neuron, and trigger an action potential, can be regarded as a meaningful neuronal assembly from the viewpoint of the reader neuron. Action potentials of other upstream neurons, which fire outside this critical time window (i.e., non-synchronously), can only be part of another assembly. The reader-integrator mechanism can therefore objectively determine whether neurons are part of the same assembly and serve
