This protocol details acute extracellular multi-unit recordings and optotagging in mice. Preparation involves setting up recording systems and optogenetic equipment. The mouse is anesthetized, placed in a stereotaxic frame, and subjected to a craniotomy for electrode placement. A multielectrode probe, combined with an optic fiber, is inserted into the target brain area. Optotagging involves light stimulation, monitored for effectiveness. Post-recording, the probe is removed and cleaned, and the mouse receives careful post-operative care to ensure recovery.