Analysis of potential contribution of spike timing to plasticity. Analysis of potential contribution of spike timing to plasticity. A, Examples of 30 overlaid traces of sequential alternate depolarizations applied to a cell during the pairing procedure (for clarity purposes, only 30 of the 60 traces evoked during the control period are illustrated). Five spikes occurred during most applied depolarizations. Arrows indicate the time of the peaks of the first and second spikes for one depolarization in each group; dashed lines extend these time points to abscissa for comparison of spike time occurrences to evoked EPSP illustrated in B. B, Average of 60 control evoked EPSPs (30 of the 60 individual records used to construct this average are shown in A) to indicate timing relationship between spikes elicited during the pairing of the applied depolarizing pulses and the EPSP onset and peak. The triangle and dashed line indicate the time of the EPSP onset as derived from the averaged fitted functions (Fig.4); the circle and dotted line indicate the time of the EPSP peak as derived from the averaged fitted functions (Fig. 4). For this example, the EPSP onset latency = 7.3 msec and the latency to peak = 21.1 msec. The results illustrated below in C-F in which the timing relationship between the spikes and the EPSP onset and peak are plotted are derived following the procedure for each cell. C, Scatter plot of individual (crosses) ratios of EPSP peak amplitudes (postpairing/prepairing ratio; ordinate) versus time between the first spike elicited during the depolarizing pulse and the EPSP onset (abscissa). Large upward triangle, circle, and downward triangle indicate mean for the LTP, NC, and LTD groups, respectively ± SD (n = 110). Mean ± SDs for the three plasticity outcome groups are -7.09 ± 2.54 msec for the LTP group, -7.50 ± 2.03 msec for the no change group, and -7.41 ± 2.40 msec for the LTD group. None of these groups are significantly different from each others (p > 0.1). D, Scatter plot of individual (crosses) ratios of EPSP peak amplitudes (postpairing/prepairing ratio; ordinate) versus time between the second spike elicited during the depolarizing pulse and the EPSP onset (abscissa). Large upward triangle, circle, and downward triangle indicate mean for the LTP, NC, and LTD groups, respectively, ± SD (n=110). Mean ± SDs for the three plasticity outcome groups are 3.64 ± 3.77 msec for the LTP group, 4.25 ± 3.89 msec for the no change group, and 4.12 ± 3.32 msec for the LTD group. None of these groups are significantly different from each other (p > 0.1). E, Scatter plot of individual (crosses) ratios of EPSP peak amplitudes (postpairing/prepairing ratio; ordinate) versus time between the first spike elicited during the depolarizing pulse and the EPSP peak (abscissa). Large upward triangle, circle, and downward triangle indicate mean for the LTP, NC, and LTD groups, respectively, ± SD (n = 110). Mean ± SDs for the three plasticity outcome groups are -19.98 ± 4.01 msec for the LTP group, -18.42 ± 3.88 msec for the no change group, and -19.24 ± 3.94 msec for the LTD group. None of these groups are significantly different from each other (p > 0.1). F, Scatter plot of individual (crosses) ratios of EPSP peak amplitudes (postpairing/prepairing ratio; ordinate) versus time between the second spike elicited during the depolarizing pulse and the EPSP peak (abscissa). Large upward triangle, circle, and downward triangle indicate grand mean for the LTP, NC, and LTD groups, respectively, ± SD (n = 110). Mean ± SDs for the three plasticity outcome groups are -9.26 ± 4.95 msec for the LTP group, -6.67 ± 5.19 msec for the no change group, and -7.70 ± 4.56 msec for the LTD group. None of these groups are significantly different from each other (p > 0.1). Iskander Ismailov et al. J. Neurosci. 2004;24:9847-9861 ©2004 by Society for Neuroscience