Delaying discharge after the stimulus significantly decreases muscle activation thresholds with small impact on the selectivity: an in vivo study using TIME
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The number of devices for electrical stimulation of nerve fibres implanted worldwide for medical applications is constantly increasing. Stimulation charge is one of the most important parameters of stimulation. High stimulation charge may cause tissue and electrode damage and also compromise the battery life of the electrical stimulators. Therefore, the objective of minimizing stimulation charge is an important issue. Delaying the second phase of biphasic stimulation waveform may decrease the charge required for fibre activation, but its impact on stimulation selectivity is not known. This information is particularly relevant when transverse intrafascicular multichannel electrode (TIME) is used, since it has been designed to provide for high selectivity. In this in vivo study, the rat sciatic nerve was electrically stimulated using monopolar and bipolar configurations with TIME. The results demonstrated that the inclusion of a 100-μs delay between the cathodic and the anodic phase of the stimulus allows to reduce charge requirements by around 30 %, while only slightly affecting stimulation selectivity. This study shows that adding a delay to the typical stimulation waveform significantly (\(P < 0.001\)) reduces the charge required for nerve fibres activation. Therefore, waveforms with the delayed discharge phase are more suitable for electrical stimulation of nerve fibres.
KeywordsFunctional electrical stimulation Multi-electrode arrays Neural interfaces Stimulation selectivity Delayed discharge
We would like to thank Mr. Guillaume Souquet from MXM Axonic for developing low-level control software of the Stim’nD stimulator, Mr. François Bonnetblanc from the DEMAR team, INRIA, for help with statistical analysis and Ms. Chloé Picq from MXM Axonic for English proof reading.
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