Fig. 3.

Noxious heat-evoked limb withdrawal and its modulation by S2 stimulation in various experimental conditions. A: baseline response latency in spinal nerve-ligated (SNL) animals that have mechanical hypersensitivity (hyper) or no hypersensitivity (nonhyper) and in sham-operated animals. B: increase of the heat-evoked response latency induced by S2 stimulation in various experimental groups. Intensity of S2 stimulation is indicated in the upper right corner of the graph. Contra, S2 stimulation contralateral to nerve injury; Ipsi, S2 stimulation ipsilateral to nerve injury; Outside, cortical stimulation outside of S2; Fake, contralateral S2 stimulation at the intensity of 0 µA. The bars show mean values, and the error bars represent SD (in A, n_hyper = 29, n_nonhyper = 8, n_sham = 14; in B, n = 12 for the Contra group, and n = 6 for all other groups). For illustrative purposes the latency data shown in B is standardized in reference to the corresponding pre-S2 latencies, but all the statistical analyses are based on raw data. In B, y-axis shows the cortical stimulation-induced increase in the withdrawal latency; 0 s represents the baseline latency before cortical stimulation and values >0 s represent increase of the latency. *P < 0.05, **P < 0.01 (Bonferroni-corrected t-test; reference: the corresponding value in the Contra group); #95% confidence interval of the cortical stimulation-induced latency does not overlap with the corresponding baseline latency.