Tarler extended his selective activation work, with the multi-contact self-sizing-spiral-cuff electrode, by conducting experiments to verify that the results were, indeed, selective activation of a single fascicle in the cat sciatic nerve. One could argue, and some did, that the resulting torque, so far reported, was actually the results of activating more than one motor fascicle and by chance the resulting torque appeared as though a single fascicle had been stimulated. This experiment draws on a phenomenon we have previously introduced, “collision block”.
In the first part of the experiment stimuli were applied to medial gastrocnemius branch Orthodromically propagating action potentials are shown as a solid line and antidromically propagating action potentials are show as dashed lines. The measured torques for two experiments are shown here.
In the next part of the experiment stimuli were applied to the 90˚ contact. Assuming the MG component of the sciatic nerve was selectively activated, orthodromically propagating action potentials shown as solid lines and antidromically propagating action potentials as dashed lines are shown. The measured torque for this experiment is shown here in the same space as the torques for the MG branch stimulation.
Next stimuli were applied simultaneously to the contact on the MG branch and the 90˚ contact on the sciatic nerve and, as happened previously, orthodromically propagating action potentials and antidromically propagating action potentials were created. But, something different happened this time, antidromically propagating action potentials collided with and annihilated the orthodromically propagating action potentials originating from the 90˚ contact, shown at a location marked with the red X. The measured torque, for this experiment, is shown in the same space as the torque measured in the previous two experiments and not here, in a different space, if something like this had occurred.
Question for you, what is the location of the red X relative to the two stimulating electrodes?
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.