Predictions for STDP curves at CA3-CA1 synapses when a single pre-synaptic spike is paired with more than two post-synaptic spikes at inter-pairing frequencies lower than the theta band.

(A) 75 pairings under the quadruplet protocol (3 post-synaptic spikes) at frequencies of 2 Hz (dotted grey) and 3 Hz (solid black). (B) 75 pairings under the quintuplet protocol (4 post-synaptic spikes) at 1 Hz and 2 Hz. The curves are indistinguishable. (C) The dynamic time constant under the quintuplet and sextuplet (5 post-synaptic spikes) protocols at 1 Hz. Post-synaptic spiking followed the pre-synaptic spike by 5 ms. (D) transients, where curves correspond to in panel C. The horizontal line shows the LTP threshold. In panels A and B, is defined as the time between the pre-synaptic spike and the last post-synaptic spike. In panels C and D, black and grey curves correspond to the quintuplet and sextuplet protocols respectively. Post-synaptic spikes were separated by 10 ms under all protocols.

(A) 2 Hz（灰色虚线）与3 Hz（黑色实线）频率下，基于四脉冲协议（quadruplet protocol）的75组配对刺激，每组包含3个突触后锋电位（post-synaptic spike）。(B) 1 Hz与2 Hz频率下，基于五脉冲协议（quintuplet protocol）的75组配对刺激，每组包含4个突触后锋电位，各组曲线无法区分。(C) 1 Hz频率下，五脉冲协议与六脉冲协议（sextuplet protocol）对应的动态时间常数，其中六脉冲协议包含5个突触后锋电位；所有突触后锋电位发放相较于突触前锋电位（pre-synaptic spike）滞后5 ms。(D) 瞬态变化，其中各曲线对应图C中的分组，图中水平线代表长时程增强（Long-term potentiation, LTP）阈值。在图A与图B中，某参数被定义为突触前锋电位与最后一个突触后锋电位之间的时间间隔。在图C与图D中，黑色与灰色曲线分别对应五脉冲协议与六脉冲协议。所有实验协议下，突触后锋电位发放之间的间隔均为10 ms。