Nonlinear dynamic analyses of single hippocampal neurons before and after long-term potentiation.

Long-term potentiation (LTP) has long been considered an important phenomenon involved in learning and memory. However, the current literature lacks systematical analyses of single neuron dynamics before and after LTP induction. In this report, we applied an up to 3rd-order Volterra kernel to analyze the dynamics of single hippocampal neurons before and after LTP induction. Broadband Poisson random impulse trains with a 2 Hz mean frequency, which included physiologically plausible patterns, were applied to stimulate CA1 pyramidal neurons through Schaffer collateral before and after LTP induction. Corresponding somatic sub-threshold excitatory postsynaptic potentials (EPSPs) were recorded from CA1 neurons using whole-cell patch-clamp recording. The result suggests that LTP increases linear responses and depresses nonlinear responses. The phenomenon can be explained with both presynaptic and postsynaptic hypotheses. Further comparisons of voltage-clamp and current-clamp recordings are needed to distinguish the changes of dynamics in presynaptic and/or postsynaptic mechanisms.