Fig. 3

The effect of referencing method on ECAP component amplitude and latency. A Representative recordings on all available recording channels demonstrate changes in ECAP magnitude with local tissue reference (LTR), differential reference (DIFF), contact 9 as reference (REF9), and contact 3 as reference (REF3). Each recording trace is a median waveform of 150 trials for a stimulation amplitude of 2.4 mA. B The influence of referencing method on conduction latency across lead recording channels. ECAP component in ESR made simultaneously across all available recording channels on the leads from caudal to rostral location (refer to Fig. 1 for more information about electrode position) with different referencing (LTR, DIFF, REF9, REF3) done virtually. Each recording trace was a median waveform of 150 trials and was normalized to itself. Dots on each trace indicate the negative peak in each channel. The dots in the first subplot using LTR are traced with a red dashed line indicating the propagation of the ECAP. The red dashed line in the following subplots are at identical slant angle and position to the one in the first subplot using LTR reference. C (Left) Illustrates ECAP propagation from channels 9 to 16 on the rostral recording Octrode™ lead. Negative ECAP peak location was detected and marked in each channel for latency measurements. Conduction velocity was estimated using a linear regression between the recording-stimulating contact distances and ECAP latency (as indicated by the dotted line). (Middle) ECAP conduction velocities were extracted and plotted at different stimulation amplitudes (1.2 to 5 mA) from five different subjects. For each subject, the density plot is shown overlayed onto a histogram. Most of the measured ECAP conduction velocities fell within the range for Aβ-fiber activation, 35-80 m/s. (Right) Radar plot shows the projection of ECAP conduction velocities with data from all subjects grouped