Comparison of generalized Hebbian rules for long-term synaptic plasticity

A large variety of synaptic plasticity rules have been used in models of excitatory synaptic plasticity (Brown et al., 1990). These rules are generalizations of the Hebbian rule and have some properties consistent with experimental data on long-term excitatory synaptic plasticity, but they also have some properties inconsistent with experimental data. For example, the BCM rule (Bear et al., 1987; Bienenstock et al., 1982) produces homosynaptic potentiation and depression, which has been observed experimentally (Artola et al., 1990; Dudek & Bear, 1992; Kirkwood et al., 1993; Fr egnac et al., 1994; Yang & Faber, 1991). But the BCM rule is also inconsistent with some experimental results; e.g., the BCM rule cannot produce heterosynaptic depression (Abraham & Goddard, 1983; Lynch et al., 1977). In addition, long-term synaptic plasticity in inhibitory pathways has been emphasized in some models of cortical function (Marshall, 1990abc, 1995a; Sirosh et al., 1996), but experimental data on inhibitory synaptic plasticity is sparse. This paper compares three popular excitatory synaptic plasticity rules { the BCM rule, the instar rule (Grossberg, 1972, 1976ab; Kohonen, 1988; Levy & Burger, 1987; Levy & Desmond, 1985; Marshall, 1995a), and the outstar excitatory rule (Grossberg, 1976c; Rescorla & Wagner, 1972) { and presents and characterizes the outstar inhibitory synaptic plasticity rule (Marshall, 1995a). These rules are evaluated by comparing their predictions with neurobiological data.