Reciprocal interactions between CA3 network activity and strength of recurrent collateral synapses.

In hippocampal slices, synchronous CA3 network activity induced persistent strengthening of active positive-feedback synapses. This altered network operation by increasing probability of future synchronous network activation. Long-term depression of synaptic strength induced by partial blockade of NMDA receptors during synchronous network activity reversed changes in probability of spontaneous network activation. These results suggest that specific network activity patterns selectively alter strength of active synapses. Stable, reversible alterations in network activity can also be effected by corresponding alterations in synaptic strength. These findings confirm the Hebb memory model at the neural-network level and suggest new therapies for pathological patterns of network activity in epilepsy.