Computations Neurons Perform in Networks: Inside Versus Outside and Lessons Learned From a Sixteenth-Century Shoemaker

Cognitive and other neural processes emerge from the interactions between neurons. Major advances have been made in studying networks in which the interactions occur instantaneously by means of graded synapses (Guckenheimer & Rowat, 1997). In other networks, the interaction between neurons involve time-delayed signals (action potentials or spikes) that activate synapses on other neurons discontinuously in a pulselike manner. These interactions can also be treated as being graded if, when appropriate, the information transmitted between neurons can be measured as the average number of spikes per unit time (Freeman, 1992); that is, the amount of information carried by individual spikes is relatively low. We refer to both of these types of interactions as “graded.” There is a large armamentarium of mathematical and dynamical systems tools for studying the computations that such neurons perform. There is also a complementary connection between these tools and biological experimentation.