Wireless navigation of pigeons using polymer-based fully implantable stimulator: A pilot study using depth electrodes

A polymer-based implantable stimulator for wirelessly navigating pigeons was conceptually suggested and a pilot study using depth electrodes was conducted. In this study, depth electrodes based on liquid crystal polymer (LCP) with eight channels were designed and fabricated. Electrochemical impedance spectrum (EIS) assessments were performed to measure impedances of the electrodes. The average value of the measured impedances was 16.8∠15.8 ° kμ. The electrodes were then advanced to a target nucleus (formatio reticularis medialis mesencephalic, FRM) of a pigeon to prove their in vivo feasibilities. Biphasic current pulses were generated by a custom-made stimulator and delivered to the electrodes to stimulate the FRM electrically. Pulses with an amplitude level of 0.567 µA, a rate of 58.0 Hz, and a duration of 1.00 ms were applied with inter-stimulus intervals of three minutes. Turning and circling behaviors were consistently shown when the FRM was stimulated. The feasibilities of the electrodes were proved in both in vitro and in vivo tests, as a pilot study for the suggested scheme. Finally, several discussions of the assessments and extensions for a fully implantable stimulator were described.