Combination of Averaged Bregma-Interaural and Electrophysiology-Guided Technique Improves Subthalamic Nucleus Targeting Accuracy in Rats

Accurate electrode implantation in the subthalamic nucleus (STN) of rats is essential for high-quality electrophysiological and neuromodulation studies but remains technically challenging due to the small size and deep location of the STN. Traditional stereotactic methods, relying on bregma or averaged bregma-interaural-based coordinates, often result in misplacement of electrode. Here, we introduce a combined anatomical and functional approach-bregma-interaural and electrophysiology-guided technique (BITE)-designed to enhance targeting accuracy for STN electrode implantation in male Sprague Dawley rats. In this method, anterior-posterior (AP), medial-lateral (ML), and dorsal-ventral (DV) coordinates are initially determined using the average of bregma and interaural references. Electrode depth (DV axis) is fine-tuned based on real-time detection of characteristic STN neuronal firing patterns. If STN featured activity is not observed on the first implantation, additional adjustments in the AP and ML axes are made, followed by electrophysiology-guided DV tuning. Using BITE, we achieved an 83% overall success rate for STN electrode implantation, with 50% of electrodes precisely located in the dorsal STN (dSTN). This represents a significant improvement compared with the bregma-based method (17%, <i>p</i> = 0.0005) and the averaged bregma-interaural-based method (40%, <i>p</i> = 0.0188). BITE offers two main advantages: (1) increased accuracy in targeting the STN and (2) improved access to the dSTN, a region of growing interest in basal ganglia research. These findings demonstrate that BITE is a reliable and effective method for precise electrode placement in the STN and may serve as a valuable tool in rat models of deep brain stimulation and basal ganglia function.