Possibilities offered by implantable miniaturized cuff-electrodes for insect neurophysiology

Recent advances in microsystems technology led to a miniaturization of cuff-electrodes, which suggests these electrodes not just for long-term neuronal recordings in mammalians, but also in medium-sized insects. In this study we investigated the possibilities offered by cuff-electrodes for neuroethology using insects as a model organism. The implantation in the neck of a tropical bushcricket resulted in high quality extracellular nerve recordings of different units responding to various acoustic, vibratory, optical and mechanical stimuli. In addition, multi-unit nerve activity related to leg movements was recorded in insects walking on a trackball. A drawback of bi-polar nerve recordings obtained during tethered flight was overlay of nerve activity with large amplitude muscle potentials. Interestingly, cuff-electrode recordings were robust to withstand walking and flight activity so that good quality nerve recordings were possible even three days after electrode implantation. Recording multi-unit nerve activity in intact insects required an elaborate spike sorting algorithm in order to discriminate neuronal units responding to external stimuli from background activity. In future, a combination of miniaturized cuff-electrodes and light-weight amplifiers equipped with a wireless transmitter will allow the investigation of neuronal processes underlying natural behavior in freely moving insects. By this means cuff-electrodes may contribute to the development of realistic neuronal models simulating neuronal processes underlying natural insect behavior, such like mate choice and predator avoidance.