Hi, Shane, Monty from the Bija Lab here. Today I'm gonna show you how to use silicon probes to perform high density electrophysiological recordings of unit activity and local field potential in the awake, behaving rat. I'll show you how to make a small micro drive a fix a, a silicon probe to it, and then implant the probe in the brain for chronic recordings.
This process is pretty straightforward, but does involve a number of steps. So let's get started. Here is a small collection of micro drives for rats and mice from moving multiple single wires, teros and silicon probes that we have designed and fabricated over the years.
Silicon probes can be attached to rigid printed circuit boards or flexible polyamide cables. We'll show you here how to affix This four shank probe to a micro drive. To prepare a drive, we need a brass plate Drill bit size 55 and 65 a tap, a single row pin header, a 0 0 90 screw and corresponding net, a drill Bit holder and a screwdriver.
The first step is to break a three pin piece from the header. Gently pull out the middle pin, enlarge a hole by drilling through it with a drill bit size 65. Then cut a thread using the ta.
Cut two pieces out of the brass plate. File the edges of the plate with a Dremel drill, a hole in the middle of both pieces using a drill bit size 55. The drive is temporarily assembled so that the brass plates Are touching the pins tighten the screws gently so that the assembly becomes stable.
The pin ends out then sold to the brass plates. The micro drive is almost ready Files a protruding end of the screw and soldiers in it to the screw. Now we have a 2 super light micro drive.
Clockwise Turning will elevate the plastic bridge. The silicon probe can be attached to the drive by two components. Silk guard elastomer weigh in.
Mix the components in a 10 to one ratio. Using a sharpened cotton applicator applies thes guard to the top end of the probe. Let it dry in an oven preheated at 60 degrees Celsius for at least two hours.
To ensure that the recording sites are devoid of any debris, the tips need to be cleaned. Prepare a four person dilution of contra detergent. Let the probe soak in the detergent at 63 degrees Celsius for at least two hours.
The detergent should be rinsed off by dipping the probe Repeatedly in distal water before fixing the probe to the drive. The impedance of each recording site should be checked using a razor blade. Cut multiple grooves into the bridge to create a rugged surface using two micro manipulators.
The probe is opposed to the bridge of the drive. The probe is then fixed to the bridge with grip cement prior to the surgery. The reference in ground electrodes are prepared.
Soldier one end of insulated copper wire for about one millimeter. Using a needle scrapes the head of a 0 0 90 stainless steel screw And sold a copper wire to it. Carefully prevent any soldier from flowing into the groove of the screw.
Cut trapezoidal pieces from copper mesh. These pieces will be assembled to protect the head stage. Surgical instrument and preparation Are the same as used in many small animal surgeries.
Please note that the surgery shown in this video is for demonstration purposes only, for appropriate visibility and filming purpose. Several prepar preparatory steps, surgical precautions and post-operative procedures are not shown here. Please consult appropriate guidelines for rodent surgery.
The entire surgery is done under gas and anesthesia using a septic conditions. After midline skin incision, the skin and periosteum are removed and the skull is cleaned and dried. The location and distance between and lambda are measured, so the X and Y coordinate of the proposition Can be determined and marked on the before opening the skull.
For implanting The probe, several screws are driven halfway into bone, both on the top and on The side of the holes are also prepared above theum to insert the electrodes. Multiple screws are critical for securing the head stage to the skull in long-term chronic experiment. Using a tiny brush, apply meta upon dentin activator over his entire surface of the skull.
Then rinse it with saline. Next, a layer of dental cement is applied carefully covering a chain course crew. The four copper flaps are then secured to this skull was grip cement.
Now we arrived at the most critical part of the surgery. The preparation of the probe implantation site using a round head drill bit. Drilling is done in multiple stages and the bone is frequently irrigated with saline.
The bone flap is carefully removed and the surface is irrigated for removing zura. Two tools are needed. The hook prepared from an insect needle and a sharp scalp of blades lift And cut it with Small bleeding can be resolved by saline irrigation.
If major bleeding occurs or if the neocortex is compromised in any way, one should consider terminating the surgery And preparing another animal. Now we are implant the silicon probe. The probe should be inserted in an area free from vessels while theto ised byline to resolve minor bleeding.
The probe is placed approximately one millimeter above the intended target. Theto is closed by applying a warm melted mixture of paraffin and mineral oil. The bottom of the drive is in Cortes skull with grip cement.
The connective part of the probe is similarly fixed to the skull. The final and critical stage of surgery is to assemble a copper mesh flaps into a protective cylinder around the probe and the drive. The cylinder also serves as an electrical shield Against environmental noise and the slow wave artifacts produced by the charged whiskers.
In the behaving animal Height can be adjusted by cutting away excess material. The wire from the reference in grounds are soldered to the appropriate pins of the connector. The ground is also soldered to the copper Mesh.
The copper meh flaps are connected by soldiering and reinforced with cement. The movement of the drive screw is tested again at the end of the surgery, A top of the head stage with a piece cut from a rubber glove after appropriate postoperative care. It's a healthy and co-operative animal that great says the next day.
To allow free Movement of the animal, we recommend to use ultralight ultra flexible multi trend wire. The slight cable requires minimum Counterbalancing and allows unrestricted movement. The quality of recording is tested each day in the home cage.
The position of the recording site is estimated by both unit firing patterns and the shape of the local field potentials. Our movie shows the implantation of a single silicone probe, but multiple site recordings using multiple probes and drives can be readily accomplished after some practice. We're also using similar but smaller drives to implant silicone probes in the mouse brain.
Lastly, silicon probe recordings can be effectively combined with local light stimulation of neural tissue in optogenetic experiments. Thank you for Watching.
