A generalized Hebbian rule for activity-dependent synaptic modifications.

In this paper our previous model of activity-dependent synaptic modification is extended and applied to a model neuron with active dendrites and is used in computer simulations to examine in detail the dependence of synaptic modifications on the interval between the onset of excitatory postsynaptic potentials (EPSPs) and postsynaptic action potentials (APs). The EPSP amplitude is increased when the action potentials occur within 20 ms after EPSPs and is reduced when the action potentials occur within 20 ms before EPSPs. Furthermore, the absolute value of changes in the EPSP amplitude tends to increase as the interval between APs and EPSPs decreases. A learning rule for synaptic modifications described in this paper may, hence, further generalize the Hebbian rule which requires conjunctive presynaptic and postsynaptic activity for synaptic modification to occur. Functional roles for such a generalized Hebbian rule are also considered.