Implanting an Electrode Array and Optic Fiber into the Mouse Hippocampus

Take an immobilized anesthetized mouse with its skull exposed.

Drill holes rostral to the coronal suture and above the cerebellum.

Insert stainless-steel screws into the drilled sites rostral to the coronal suture for implant stabilization.

Insert the ground and reference screws above the cerebellum to minimize electrical noise.

Cover these screws with cement to prevent muscle artifacts during the recordings. Secure the other screws with cement.

Drill holes in the skull, exposing the hippocampal tissue. Apply saline to maintain tissue hydration. 

Lower the optic fiber and electrode array through the holes into the hippocampus for optical stimulation and targeted neural activity recording.

Apply warm wax around the implantation site to protect the tissue.

Encase the implant and skull in cement to stabilize them.

Solder the ground and reference wires to the electrode array to ensure a stable electrical connection.

Cover the wires with cement.

Return the mouse to its cage for recovery.

Begin by drilling four holes of 0.8 millimeters diameter in the cleaned skull of the anesthetized animal. Drill two holes rostral to the coronal suture and two above the cerebellum. Next, place stainless steel bone screws for grounding and stabilization of the implant. Position the ground screw connected to a copper wire above the cerebellum. Cover the ground screw completely with cement to prevent muscle artifacts during the electrophysiological recordings.

Build a cement ring connecting all screws. Perform a craniotomy above the implantation site. Then, apply approximately 1 microliter of sterile saline on the surface of the brain tissue. Use the stereotax to slowly lower the wire array into the craniotomy. Then, apply approximately 5 microliters of warm liquid wax above the implantation site to protect the brain tissue. Apply cement around the wire array and cover the skull with cement. Apply one drop of flux to the pre-soldered ground wire or the pre-soldered wire connected to the ground screw and fuse the wires using a soldering machine. Lastly, cover the entire ground wire with cement.