Synapse signalling complexes and networks: machines underlying cognition.

All thoughts and actions are encoded in patterns of neuronal electrical activity. Circuits of nerve cells connected by synapses are dedicated to processing information in these patterns. Information is not only transmitted across the synapse but also monitored by postsynaptic molecular machines. These machines are macromolecular complexes of approximately 100 proteins organised into a network of protein interactions. The network can be mathematically described as a scale-free network. Components of the complexes are necessary for decoding the neural code and converting electrical information into biochemical changes. The network properties of these complexes may explain many of the features of neuronal plasticity and cognitive function in rodents. Importantly, these multiprotein complexes and their network properties shed new light on the basis of human cognitive diseases including schizophrenia, autism, Huntington's disease and mental retardation. Supplementary material for this article can be found on the BioEssays website http://www.interscience.wiley.com/jpages/0265-9247/suppmat/index.html.