Figure 1

Schematic representation of the three stimulation patterns used. Bottom train (CFT50) is a constant-frequency train with all interpulse intervals equal to 50 ms; middle train (VFT50) is a variable-frequency train with an initial doublet of 5 ms and remaining pulses equally spaced by 50 ms; and top train (DFT50) is a doublet-frequency train with 5-ms doublets separated by interdoublet interval of 50 ms. Each train's name is based on the duration of the longest interpulse interval within that train. Each train has a maximum of 50 pulses (not shown in figure) and a pulse width of 600 μ s.