Induction of sharp wave-ripple complexes in vitro and reorganization of hippocampal networks

Hippocampal sharp wave-ripple complexes (SPW-Rs) occur during slow-wave sleep and behavioral immobility and are thought to represent stored information that is transferred to the neocortex during memory consolidation. Here we show that stimuli that induce long-term potentiation (LTP), a neurophysiological correlate of learning and memory, can lead to the generation of SPW-Rs in rat hippocampal slices. The induced SPW-Rs have properties that are identical to spontaneously generated SPW-Rs: they originate in CA3, propagate to CA1 and subiculum and require AMPA/kainate receptors. Their induction is dependent on NMDA receptors and involves changes in interactions between clusters of neurons in the CA3 network. Their expression is blocked by low-frequency stimulation but not by NMDA receptor antagonists. These data indicate that induction of LTP in the recurrent CA3 network may facilitate the generation of SPW-Rs.