Effects of presynaptic and postsynaptic resource redistribution in Hebbianweight adaptation

The Hebbian hypothesis of activity-dependent synaptic plasticity has gained much support from experimental studies of long-term potentiation and depre ssion. Such studies have also uncovered complex patterns of competition amo ng the synapses. Such effects may be due to the neuron redistributing its l imited synaptic resources as synaptic strengths change. In computational mo dels this strategy is commonly known as normalized Hebbian learning. Howeve r, not much consideration is usually given to whether the weights are norma lized over the presynaptic or the postsynaptic sites of the neuron. Our res ults show that the different loci of normalization can result in drastic di fferences in the model's behavior, suggesting that future experiments shoul d investigate presynaptic factors of redistribution as well as the more wid ely studied postsynaptic factors. (C) 2000 Elsevier Science B.V. All rights reserved.