Biological Evidence for Synapse Modification, Relevant for Neural Network Modelling

Abstract

Evidence from experiments in the literature is presented for the mechanisms which contribute to the modifiability of synapses under the influences of local conditions in a neuronal net. However, there is always the complication that experiments in living beings or in cultured neural tissue allow interference only at a macroscopic scale. Therefore the experimental conditions in the referenced literature are described sufficiently carefully that the conclusions drawn from them can be appreciated well enough. After a brief survey of which synaptic properties are in principle variable, long—term potentiation (LTP) is described first, in a historical context. The role of nitric oxide, NO, is then demonstrated along the experiments of Rose et al. on food discrimination learning in chicks. Finally, the role of electrical activity is shown according to the famous experiments in Nelson's group on cell cultures of the spinal cord of mouse fetuses. In all cases the NMDA type of glutamate receptor plays an essential role.