When thinking about building clinical systems that will deploy a multi-contact-self-sizing-spiral-cuff electrode, confidence needs to be established that the technology will work when placed in humans. Confidence, in this case, comes through animal experiments. The work here is geared toward devices employed in the motor system, though insights gained here could apply to devices used to exert control of any system in the body. The experiments performed by Tarler, and described here, were to test the likelihood that any one of the four motor fascicles, in the cat sciatic nerve, could be selectively activated with a four contact self-sizing-spiral-cuff electrode.
There were nine acute experiments performed, listed in the left-hand column. The four target branches are listed in the top row. Place holders for the four, radially place contacts are indicated here. Noting the legend at the bottom, a blue circle with a minus sign indicates successful recruitment with a cathodic current applied to a single contact. A green circle indicates successful recruitment after field steering was applied, a minus sign for cathodic steering and a plus sign for anodic steering. The cross hatched circles indicated no steering was attempted because of time constraints in the experiments; the experiments were long and pushed the endurance of the human and animal. Four red circles indicate that steering was attempted but failed to produce selective activation.
These results indicate that, by chance, one of the four radially spaced contacts was sufficiently close to a target fascicle that full selectivity could be obtained with monopolar cathodic stimulation, and in one case selective activation was achieved without the need of field steering. A total of 23 candidate fascicles out of 36 possible were selectively activated with just monopolar cathodic stimulation. with the application of steering currents the number of selectively activated fascicles increased to 33 out of 36. The three remaining fascicles were not attempted due to time constraints.
These acute experiments were deemed to imply that a four contact self-sizing-spiral-cuff electrode would likely yield selective activation of any one of four fascicles contained in the compound nerve.
Tarler, M.D. and J.T. Mortimer, “Selective and Independent Activation of Four Motor Fascicles Using a Four Contact Nerve Cuff Electrode”, IEEE Trans. on Rehabilitation Engineering, Vol 12, pp251-257. 2004.