Primed Burst Potentiation: Lasting Synaptic Plasticity Invoked by Physiologically Patterned Stimulation

Long-term potentiation (LTP), a lasting increase in synaptic efficacy seen following high-frequency stimulation, has been extensively studied as a mnemonic model. However, a major conceptual difficulty in relating LTP to an endogenous mechanism for memory formation is that the parameters commonly used for its induction are well beyond the normal physiological firing range of hippocampal neurons: usually 50–400 stimuli, delivered at frequencies of 100–400 Hz, are employed (Teyler and Discenna, 1984). While hippocampal pyramidal cells are known to discharge in “complex-spikes”, consisting of several action potentials at frequencies greater that 100 Hz, groups of 3 or 4 action potentials are most commonly seen (Suzuki and Smith, 1985); continuous high frequency discharge is only observed under experimentally-induced or pathological conditions. We considered the possibility that the threshold for the induction of LTP might be reduced if the pattern of stimulation more accurately reflected normal neuronal firing