A Method of Flexible Micro-Wire Electrode Insertion in Rodent for Chronic Neural Recording and a Device for Electrode Insertion

Reliable chronic neural recording from focal deep brain structures is impeded by insertion injury and foreign body response, the magnitude of which is correlated with the mechanical mismatch between the electrode and tissue. Thin and flexible electrodes cause less glial scarring and record longer than stiff electrodes. However, the insertion of flexible microelectrodes in brain has been a challenge. Here, a novel insertion method is proposed, and demonstrated, for precise targeting deep brain structures using flexible micro-wire electrodes. The microelectrode is spun and slowly inserted in brain through an appropriate electrode guide. The electrode guide does not penetrate into cortex. Based on two new mechanisms, namely spinning and guided insertion, we have demonstrated successful insertion of 25-micron platinum flexible electrodes about 10-mm deep in rat brains without buckling. We present an electrode insertion device based on the proposed method and demonstrate its use to implant flexible microelectrodes in rat brains. The step-by-step insertion process is described. Microelectrodes were inserted in the Bötzinger complex and respiratory neural activity was recorded acutely in nine rats and chronically in two rats for 50 days.