Electrophysiological recording from a chronic chamber-implanted non-human primate
Robert S Turner, Witold J Lipski, Daisuke Kase, Devin R Harsch
Abstract
This protocol describes the preparation and insertion of extracellular recording electrodes into intracranial targets of a non-human primate implanted with a chronic recording chamber. A piercing guide cannula is used to penetrate the dura and to guide the electrode. Practices related to targeting, electrode cleaning, and electrode movement and settling relative to brain tissue are discussed.
Steps
Preparation before the day of recording
Choose the target area using resources such as an MRI or prior brain mapping.
Calculate the distance from the micro-drive to the surface of the brain.
Draw a mark on the dura piercing guide at the calculated distance from the tip.
Mount an electrode or multi-electrode-array on the micro-drive.
Cover the micro-drive and leave a message for other lab members to exercise caution when working near the micro-drive to avoid accidental damage.
Preparation before chairing the animal
Check that the recording system is working properly.
Clean the electrode and piercing guide (follow the instructions for the specific electrode in use). For our recordings, we soak the electrode and piercing guide in a 1% solution of enzymatic detergent (Metrex, EmPower Dual-Enzymatic Detergent) for 30 minutes, followed by multiple rinses with sterile water, and then another rinse with saline.
Preparation after chairing the animal
After chairing the animal, secure the animal with restraints such as arm restraints and a neck-plate.
Secure the animal's head using head-fixation posts.
Wipe the surface of the implant with a sani-cloth (PDI health care).
Clean the recording chamber (see our other protocol).
Fill the chamber with saline so that any tissue is not exposed to air.
Transfer the animal into the recording rig.
Piercing the dura and lowering the electrode
Rinse the electrode and piercing guide with sterile water and saline.
Mount the micro-drive on the animal’s head.
Connect the micro-drive to the depth monitor if available.
Check/note the offset of the electrode if the depth on the monitor is not zero.
Connect the electrode to the recording system.
Lower the piercing guide to the marked depth (surface of the dura).
Lower the electrode 1-2 mm above the dura with coarse drive.
Start monitoring the signal from electrode.
Start lowering the electrode with the fine drive until researchers can confirm the spike activity.
Continue lowering the electrode to the target depth.
Lower the electrode 0.5 to 1 mm below the target depth.
Wait for 10 minutes (it is recommended to let the animal do a behavioral task or to give reward to the animal during this period. Movement of the face and jaw aids in settling the electrode).
Pull up the electrode to the target depth.
Wait for 50 minutes. This is especially important when recording from deep structures to account for any potential movement of the brain that occurred while lowering the electrode.
Start the recording.
After the recording
Pull up the electrode slowly all the way.
Pull up the piercing guide.
Unmount the micro-drive.
Move the animal from the recording chamber to the place for chamber cleaning.
Clean the chamber as outlined in our other protocol.
Put the chamber cap back on the chamber.
Return the animal to its home cage.
Clean the electrode and piercing guide (follow the instructions for the electrode being used).
