Figure 6.
A, Comparison of two STDP protocols (Δt = 10 ms and Δt = −30 ms between EPSP and AP, respectively) and the resulting amount of plasticity (EPSP amplitude in percentage of control) in control conditions and in the presence of SCH-23390, sulpiride, and d-AP-5. Diagram also contains dataset in which the STDP protocol contained an AP burst. Bars represent mean ± SEM. For statistical tests, EPSP changes 20–30 min after application of the respective STDP protocol were compared between groups (one-tailed Student's t test, *p < 0.05). B, Plot of single experiments using STDP protocols (Δt = 10 ms and Δt = −30 ms, respectively) in control conditions (open circles) and in d-AP-5 (50 μm, crossed circles). Bars show the respective group averages. C, Analysis of PPR and CV of EPSPs. Top, Analysis of paired pulse ratio before (PPRb) and after (PPRa) the respective STDP protocols. Same cells and experimental conditions as in A. PPRs were plotted against the ratio of EPSPs after (EPSPa) and before (EPSPb) the respective STDP protocols (Δt = 10 ms, red; Δt = −30 ms, blue). No significant change in PPRs occurred (paired two-tailed Student's t test). Bottom, Coefficient of variation of EPSPs was calculated before (CVb) and after (CVa) the respective STDP protocols (Δt = 10 ms, red; Δt = −30 ms, blue). Significant changes in CVs are indicated (*p < 0.05, paired two-tailed Student's t test). For comparison, inset shows the relation of the squared CV ratios to EPSP ratios, a plot in which the location of data points allows an interpretation of which synaptic parameter (n, p, or q) has changed after plasticity (Bekkers and Stevens, 1990; Malinow and Tsien, 1990; Manabe et al., 1993). When the EPSP ratio is bigger than 1 (LTP), points located above the diagonal line indicate an increase in p and/or n, and points located on the horizontal dashed line indicate an increase in q. The same is true for the case of an EPSP ratio smaller than 1 (LTD), only that points located below the diagonal indicate a decrease in p and/or n.