TITLE: Essential surgeries for the electrophysiological recording from a behaving non-human primate brain 1 (Head fixation post and recording chamber implantation)
AUTHORS: Daisuke Kase, Witold J Lipski, Devin R Harsch, Robert S Turner

[DESCRIPTION]
The implantation of a head fixation post and recording chamber is the first step to performing electrophysiological recording of head-restrained awake non-human primates. Implants can last for many years if there are no infections. However, they may fail in a few months if an infection occurs, especially between the implant and the skull. Therefore, performing surgical procedures under strictly sterile conditions is the key to the successful progress of the project.

[STEPS]
SECTION: Planning for the head fixation post and recording chamber implantation
1. Calculate the coordinates of the target brain area relative to the ear bar zero.

 

   
   

SECTION: Planning for the head fixation post and recording chamber implantation
2. Attach the chamber holder  bar to the stereotaxic arm.
   

SECTION: Planning for the head fixation post and recording chamber implantation
3. Mount the stereotaxic arm onto the stereotaxic calibration frame.
  

SECTION: Planning for the head fixation post and recording chamber implantation
4. Adjust the angle of the stereotaxic arm if necessary.
  

SECTION: Planning for the head fixation post and recording chamber implantation
5. Move the stereotaxic arm so that the tip of the chamber holder points at the target coordinates (except for the AP) calculated in Step 1.
  

SECTION: Planning for the head fixation post and recording chamber implantation
6. Note the positions of the stereotaxic frame and arm (AP coordinate on the rail of the frame, ML coordinate on the stereotaxic arm, and angle of the stereotaxic arm).
  

SECTION: Preparation on the day before the surgery
8. Bring all sterile tools to the surgical suite and check to ensure nothing is missing.

 

SECTION: Preparation on the day before the surgery
9. Check if the animal is on NPO.
SECTION: Preparation in the prep room on the day of surgery
10. Sedate the animal.
SECTION: Preparation in the prep room on the day of surgery
11. Shave the animal’s hair.
SECTION: Preparation in the prep room on the day of surgery
12. Start the gas anesthesia.
SECTION: Preparation in the prep room on the day of surgery
13. Transfer the animal to the surgical suite.
SECTION: Surgical procedure in the surgical suite
14. Fix the animal’s head on the stereotaxic frame.
SECTION: Surgical procedure in the surgical suite
15. Wipe the surface of the animal’s head with Betadine and Ethanol.
SECTION: Surgical procedure in the surgical suite
16. Scrub both arms (5 min per arm).
SECTION: Surgical procedure in the surgical suite
17. Put on a sterile surgical gown.
SECTION: Surgical procedure in the surgical suite
18. Put on sterile gloves.

 

SECTION: Surgical procedure in the surgical suite
19. Put sterile surgical drapes onto all of the animal's body, except for the head (expose the clean surface prepared in Step 14).
SECTION: Surgical procedure in the surgical suite
20. Cut and remove the skin (usually in a round shape), and expose the skull.
SECTION: Surgical procedure in the surgical suite
21. Remove all soft tissue from the surface of the skull.
SECTION: Surgical procedure in the surgical suite
22. Cut the drape on the animal’s body around the rail of the stereotaxic frame to mount the base part of the stereotaxic arm.

 

SECTION: Surgical procedure in the surgical suite
23. Mount the base unit of the stereotaxic arm at the preliminary chosen coordinate.

 

SECTION: Surgical procedure in the surgical suite
24. Since the rail is still exposed, we want to cover the rail of the stereotaxic frame with a new sterile drape, so that no unsterile surface is exposed. Again, please ensure to not touch the unsterile rail.
SECTION: Surgical procedure in the surgical suite
25. Mount the main unit of the stereotaxic arm onto its base unit.
SECTION: Surgical procedure in the surgical suite
26. Mount the chamber on the stereotaxic arm and move the chamber as close to the skull as possible.
SECTION: Surgical procedure in the surgical suite
27. Draw a line on the skull around the chamber.
SECTION: Surgical procedure in the surgical suite
28. Unmount the main unit of the stereotaxic arm and store it on a sterile surface.
SECTION: Surgical procedure in the surgical suite
29. Now, surgeons can check if the incision of skin is large enough. Make sure there is enough exposure of the skull to build a dental acrylic implant.

 

SECTION: Surgical procedure in the surgical suite
30. Detach the connections between the muscle and skin and between the muscle and skull.
SECTION: Surgical procedure in the surgical suite
31. Remove the muscle with electrocautery if the muscle is too close to the implants.

 

SECTION: Surgical procedure in the surgical suite
32. Put a drill bit in the pin vise, and expose the drill bit about 3-4 mm from the pin vise to prevent the surgeon from making too deep of a hole and damaging the dura and brain.
SECTION: Surgical procedure in the surgical suite
33. Make a hole in the skull by slowly turning the pin vise.

 

SECTION: Surgical procedure in the surgical suite
34. If the drill bit does not pierce the skull and the researchers cannot confirm the surface of the dura, expose the drill bit a little more from the pin vise and continue drilling the same hole until the drill bit pierces the skull.
 

SECTION: Surgical procedure in the surgical suite
35. Check the thickness of the skull from the length of the exposed drill bit.
SECTION: Surgical procedure in the surgical suite
36. Put a bone screw into the drilled hole and screw it in.

 

SECTION: Surgical procedure in the surgical suite
37. Repeat steps 32-35 until enough bone screws are implanted.
SECTION: Surgical procedure in the surgical suite
38. Remount the stereotaxic arm (and chamber) onto the base unit.
SECTION: Surgical procedure in the surgical suite
39. Make sure there is no blood or tissue on the skull, only a dry surface (and screws).
SECTION: Surgical procedure in the surgical suite
40. Move the chamber close to the surface of the skull.
SECTION: Surgical procedure in the surgical suite
41. Put the dental acrylic to cover the bone screws and the wall of the chamber.

 

SECTION: Surgical procedure in the surgical suite
42. Check to ensure all dental acrylic around the chamber is hard and that the chamber is secured in the dental acrylic.
SECTION: Surgical procedure in the surgical suite
43. Loosen the screw on the chamber holder, and unmount the stereotaxic arm.
SECTION: Surgical procedure in the surgical suite
44. Mount the head fixation post on the stereotaxic arm through the head fixation post holder, and mount the arm onto the base unit.
SECTION: Surgical procedure in the surgical suite
45. Move the head fixation post close to the dental acrylic.

SECTION: Surgical procedure in the surgical suite
47. Optional procedure – if the researchers will use a chamber adapter for the recording, this is the best timing to align the mediolateral and anteroposterior axes with the stereotaxic coordinates.
SECTION: Surgical procedure in the surgical suite
48. Unmount the stereotaxic arm.
SECTION: Surgical procedure in the surgical suite
49. If the skull is exposed, researchers need to tighten the edge of the skin.
SECTION: Surgical procedure in the surgical suite
50. Make a V-shape incision on the edge of the skin, and suture the sides of V.
SECTION: Surgical procedure in the surgical suite
51. Put the chamber cap onto the chamber.
SECTION: Surgical procedure in the surgical suite
52. Stop the gas anesthesia and wait for the animal’s recovery.
SECTION: Surgical procedure in the surgical suite
46. Put dental acrylic around the head fixation post to bridge the existing dental acrylic and the head fixation post.

 

SECTION: Planning for the head fixation post and recording chamber implantation
7.  <Optional>
Secure a dummy skull on the stereotaxic frame, and transfer the stereotaxic arm to the stereotaxic frame to check the position of the chamber on the skull.