Synaptic Currents, Neuromodulation, and Kinetic Models

Linking this article to brain theory are questions regarding generalizations to other discharges and synapses, long-term changes (neuromodulation, plasticity), participating membrane and molecular mechanisms, and the roles of deterministic issues and noise. Coding fidelity is useful biologically in some sensory or motor situations (although not always); its compensation poses an interesting problem. Behaviors are reproduced satisfactorily by models, mainly formal and incorporating variables recognized in living preparations that refer to presynaptic spikes, thresholds, currents, conductances, and so forth. Models ignore issues such as the neuron's regional inhomogeneity and the individual synapse's complexity. Circuit-oriented concepts are indispensable for understanding nervous systems. Synapses are operational units therein, but claiming their hegemony is similar to claiming that the atom holds the key that unravels the universe. However, the relative significance of the whole should not be exaggerated. Synaptic coding and neuronal entrainments, although not sufficient, are indispensable for comprehending neural networks and the nervous systems that they are intended to mimic. Networks with simple units reveal surprisingly complex behaviors; those with more realistic units show great promise and will add important dimensions to the body of knowledge (Aihara, Takabe, and Toyoda, 1993). In: Michael A. Arbib CEd-1 The Handbook o f Bra in Theorg & Neural Networks, Cambridge, MA: MIT Press 1995