Stereotactic system for accurately targeting deep brain structures in awake head-fixed mice

Abstract

Deep brain nuclei, such as the amygdala, nucleus basalis, and locus coeruleus, play a crucial role in cognition and behavior. Nonetheless, acutely recording electrical activity from these structures in head-fixed awake rodents has been very challenging due to the fact that head-fixed preparations are not designed for stereotactic accuracy. We overcome this issue by designing the DeepTarget, a system for stereotactic head-fixation and recording, which allows for accurately directing recording electrodes or other probes into any desired location in the brain. We then validated it by performing intracellular recordings from optogenetically-tagged amygdalar neurons followed by histological reconstruction, which revealed that it is accurate and precise to within [~]100 m. Moreover, in another group of mice we were able to target both the mammillothalamic tract and subthalamic nucleus. This approach can be adapted to any type of extracellular electrode, fiber optic or other probe in cases where high accuracy is needed in awake, head-fixed rodents. Highlights> The Deep Target, new system for accurately targeting deep nuclei in head-fixed animals for electrophysiology and optogenetics. > Accurate and precise to within 100 m following a one-time alignment. > Validation: Opto-tagged Vm recordings in the amygdala of awake mice. > Validation: Targeting multiple deep brain structures in the same mouse.