The Predictive Brain: Temporal Coincidence and Temporal Order in Synaptic Learning Mechanisms

Abst rac t Some forms of synaptic plasticity depend on the temporal coincidence of presynaptic activity and postsynaptic response. This requ i rement is consistent with the H bbian, or correlational, type of learning rule used in many neura l network models. Recent evidence suggests that synaptic plasticity may depend in part on the product ion of a membrane permeant-diffusible signal so that spatial volume may also be involved in correlat ional learning rules. This latter form of synaptic hange has been called volume learning. In both Hebbian and vo lume learning rules, interact ion among synaptic inputs depends on the degree of coincidence of the inputs and is otherwise insensitive to their exact temporal order. Condit ioning exper iments and psychophysical studies have shown, however, that most animals are highly sensitive to the temporal order of the sensory inputs. Mthough these exper iments assay the behavior of the entir