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. Author manuscript; available in PMC: 2016 May 24.
Published in final edited form as: Eur J Pain. 2009 May 23;14(2):222–225. doi: 10.1016/j.ejpain.2009.05.001

Fig. 2.

Fig. 2

Regression lines for tramadol (black) and placebo (red) sessions. In the placebo session the slope was never significantly different from zero. In the tramadol session the slope was significantly different from zero for all the three LEP components, but the N2 and P2 slopes were steeper than that of N1 (p < 0.001).