Spike-sorting, before /after

This uses the automated method Klustakwick and then some manual refinement

#PlaceCells #SpikeSorting #Tetrodes #Neuroscience

⤵️​ We have signals! I think… I’ve never implanted that high in cortex. It’s definitely very silent for now. Does it look normal to you?
The timescale is 2s; this shows the unfiltered and unreferenced signals. There are a few disconnected channels.

After trying it out, I still don’t understand the point of implanting your #Tetrodes out of the brain and wait until the end of the surgery to lower them. I much prefer watching them go in the brain, so I know what’s happening! And it’s also much faster.

⤵️​ Giving the final touches to the #HybridDrive

In more details:

1. Adding the cone
   (painted with conductive epoxy, connected to the drive’s ground, to (try and) shield it from electrical interference, but it’s the first time I do this so I don’t know if it will work. Once on the rat, it will have a cap as well, except when plugged into the recording system.)

2. #GoldPlating
   This drive has 2 sets of tetrodes: 13 microns Nichrome wire and 17 microns Platinum-Iridium wire (testing which is best). Due to different wire material and diameter, they get gold-plated slightly differently; see this for a good plating tutorial for 12-13 um Nichrome, generously shared by John Bladon: https://github.com/elduvelle/ephys_tutorials/blob/main/4_gold_plating_Nichrome_12um.md

3. View of the finished drive.
   I am also testing the effects of implanting the tetrodes directly in the brain during surgery, or keeping them retracted in the drive and only lower them at the end of the surgery. This is for a bilateral dorsal #Hippocampus implant so it has two groups of tetrodes. I personally do not understand the point of not implanting directly in brain…

4. The guide/outer cannulas and their #Tetrodes
   Each guide cannula holds 4 tetrodes which move together, excepted 1 cannula that holds a single tetrode - to be left in the corpus callosum and used for reference. If everything works as planned. I used 27 gauge (thin walled) inner cannulas to guide the tetrodes - the smaller diameter that you can see); these do not move, only the shuttles and the tetrodes move.

Next step is implantation surgery!

@chrisXrodgers Yes - that's the idea! But not everyone likes them, some prefer non-serrated scissors. At the moment I use serrated for bundles between 1-4 tetrodes and flat for larger bundles. Here's an example of a bundle of 8 #Tetrodes :

⤵️​ my favourite view: nicely cut #Tetrodes! (Diameter may be 13 or 17 microns)

Here’s what I’m working on at the moment: a 32 #Tetrodes “hyperdrive” for bilateral hippocampal recordings. It’s a prototype - I’ll let you know if it works...🤞​

2/
Here are some interesting tables from it...
I wonder how well it works with #Tetrodes and in the #Hippocampus given the special shape of #ComplexSpikes 🤔​

If you try it please let us know what you think!!

#Kilosort #Electrophysiology #SpikeSorting
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@chrisXrodgers
Very good question!
I have most recently used MountainSort + Phy (via SpikeInterface) and I quite like Phy (for manual refinement of clusters) but not so much Mountainsort - it seemed very conservative. I’ll go back to it soon and tweak the settings a bit. If you want to try it out we have some shared code with the Genzel lab here: https://github.com/elduvelle/SpikeinterfaceMS4_GenzelLab

But I was also going to try out Kilosort. Do you really not like it?
Before that KlustaKwik + Tint has been the gold standard for me :) … but maybe it’s time to move on!
#SpikeSorting #Tetrodes #Electrophysiology