Alternating dominance of NMDA and AMPA for learning and recall: a computermodel

Physiological studies reveal a dichotomy in biological Hebbian learning: NM DA receptors are utilized for induction of long term potentiation (LTP) whe reas AMPA is used for LTP expression. We propose that this dichotomy would have functional value: preventing previously stored memories from interferi ng with the storage of new memories. A previous hypothesis reduces this int erference by temporarily reducing associative weights during learning. Comp lementary to this model, we propose a dual transmission algorithm in which one set of synaptic weights are used primarily for learning and another pri marily for recall. This algorithm shows good performance in a simple neural network model. Biologically, the model could be mediated by a cholinergic switch from dominance of learning-insensitive NMDA receptors to dominance o f learning-modifiable AMPA receptors. NeuroReport 12:2503-2507 (C) 2001 Lip pincott Williams & Wilkins.