Fig 9. Microstimulation Thresholds for Eliciting Cockroach Leg Deflection.

Electrodes were first placed in the coxa and femur and connected to modified audio cables plugged into an iPhone 5s running the “Tone Generator” App. The volume necessary (threshold) to cause visible leg movement at two electrical sine wave frequencies was then measured. The coxa electrode was subsequently moved alongside the femur electrode, and thresholds tested again. Finally, the coxa was removed with forceps, and thresholds measured similarly. Thresholds were significantly higher with both electrodes in the femur (bipolar configuration) versus one electrode in the coxa and the other in the femur (monopolar configuration). There was not a significant difference in thresholds between the coxa present and coxa absent conditions with both electrodes in the femur. Thresholds were measured in 8 legs during the three conditions and then averaged. Voltage output of iPhone was measured with an oscilloscope and is also reported next to threshold values. * = p<0.05.