Instructions for 8 tetrode (32 channel) megadrive

Transcription

1 Instructions for 8 tetrode (32 channel) megadrive List of parts Body Lid Base Shuttles Gold pins Cannula (Cooper s Needle Works, O/N: CK961288, DRG/NO: 33GX12) 12.5um wire Screws List of tools needed Essential Ruler Needlenose pliers Supersharp scissors for cutting electrode tips

2 Decide on the arrangement of electrodes cannula The first step is to decide if you want to modify the position of the holes guiding the electrodes. There are holes in the bottom part of the drive and they will guide your electrode to the right brain region(s). In the picture at right, you can see a bottom part that was modified to perform dual-site recordings. That was done by drilling a new hole into the bottom part of the drive and fixing a guiding cannula with dental acrylic. Insert the insect pins Insert insect pins into the bottom part of the microdrive. There are a total of 20 pins to insert and the head of the pin should point towards the bottom of the drive. They should come out of the bottom drive by about 1.5 cm. Trim shuttle and mount with watch makers forceps Mount the shuttles onto the pins The shuttles will allow you to move the tetrodes up and down independently. They come in two different shapes: short and long. The short ones go in the middle of the drive, and the long ones on either side. There are two pins for each shuttle.

3 Add the middle part of the microdrive Cover the shuttles with the middle part of the drive. The 20 pins have to be aligned with the 20 holes in the middle part. White shuttles should be at the top (red arrow). For ease, align the four corner pins first. Add the 8 screws The 8 screws need to go through the shuttles. Turning the screw counter-clockwise will lower the shuttle and therefore your electrode. Don t let screws push shuttles down, use forceps underneath as leverage. Make sure screws bite into shuttles, so that turning the screw raises and lowers the shuttle. Insert the cannula (pre-made) into the shuttles Insert a cannula through the holes at the bottom part of the drive and up into the hole at the end of each shuttle to avoid bending. Leave about 0.5mm of cannula above the top of the shuttle. Once they are all in place, glue the cannula to the shuttles with 5min epoxy (mix on glass lid and apply with needle). Notice in the photo there is one tube glued to the outside of the shuttle (red arrow). This was done to reduce the bend in the cannula (excessive bend due to cannula redirected to different brain region).

4 Put four gold pins in the holes in the lid Put four gold pins in the four holes in the center (5 th row down) of the top of the lid (Fig A). Insert through the top of the lid (Fig B) and use needle-nose pliers to push all the way down until the tips stick out the bottom (Fig C). Add a bit of solder to each of the two sets of pins (Fig C) before soldering a thin bit of wire to connect the two pairs (Fig C). Solder an insulated ground wire of desired length (green in Fig D) to the crossconnected wire (grey in Fig D). Finally, cover the cross-connecting wire and solder with nail varnish. Note: keep this as neat and lowprofile as possible to prevent the ground wire from bumping into the shuttles. Put the lid on the insect pins Cut a small notch in the plastic of the middle part of the drive to allow your ground wire to eventually poke out. Push the pins to that they come up about 1.7 cm and then add the lid on top of the pins. Push on the lid so that it is approximately 1.2 cm above the middle part of the drive. ~1.2cm

5 Load and glue the tetrodes Insert superfine wire into each cannula to make sure it is clear. Prepare the tetrodes (California Fine Wire Co., size (12.5micron), Tungsten 99.95%, HFV insulation): cut lengths of ~25cm and twist as you would for a normal implant. Apply heat gun at 190 for 20sec. Leave free wire tips a bit long and don t strip/burn insulation off of them. Load your tetrodes into the cannula. The 4 free wires of the tetrode go into 4 holes in the lid according to the wiring diagram at the end of these instructions: 1) grasp the tetrode by the tip of the bundled end (which will be cut off later) and insert into cannula 2) gently nudge down little by little with forceps 3) flip whole mega-drive upside down and insert free wires into the holes in the lid 4) when finished with the four tetrodes on one side, turn the drive around and do the next four Make sure that all the tetrodes come out at the bottom before gluing the tetrode (with 5min epoxy) to the cannula sticking out of the shuttle Lower the top to the final position and remove pins Bend and detach both ends of the pins as they come out of the top and bottom parts of the drive. Remove the bottom pins first, epoxy the ends and then remove the top bits to prevent them from coming out entirely. Either bend them back and forth until they snap off, or use pliers. Note: excessive force from the pliers may cause damage to the drive. Lower the tetrodes to the lowest position Turn the screws counter-clockwise to the lowest point. This is extremely important, failure to do so will mean that you won t be able to move the tetrodes. Be careful not to over-screw the screws by turning them too much or you will strip the threading on the plastic and won t be able to move your tetrode. Put the gold pins in the holes of the lid Insert gold pins into each of the holes; each pin should make contact with the tetrode wire. Use needle-nose pliers to push pins in all the way; in theory, this should crush the insulation and allow the pin to touch the wire directly. When finished with all the pins, snap (with forceps) the excess tetrode wire that comes out to prevent short-circuits.

6 Final cut and gold plating Cut each tetrode bundle individually to the final depth at which you need to implant. Note: when you raise the tetrodes back to the top position, ~3mm will retract into the drive; make sure your total tetrode length exceeds 3mm. Follow gold plating protocol. Return tetrodes to top position Turn the screws clockwise almost all the way to bring tetrodes to the top position. Leave about 2 turns of the screw left in case the drive is implanted lower than expected and the tetrodes need to be raised a bit. Drive is now loaded.

7 WITHOUT ADAPTOR White marks on headstages are at this end T3 T4 T7 T T2 T1 T6 T5 CH1-16 headstage CH17-32 headstage