#Neuroscience#Ephys question: anyone recognize these signals? The wavy thing? It’s supposedly in rat cortex (above hippocampus), when the rat is immobile, possibly sleepy. Recorded with #Tetrodes.
The x-axis scale for each of the two columns is 1s. #Electrophysiology
If it’s ~10hz - we saw stuff like this in some of Brendon Watson’s frontal cortex dataset. Some rats had a bunch, others had none. Gyuri always called them high voltage spindles and said they were either a kind of epilepsy or something very important that no one understood. Always during drowsiness at the transition from wake to NREM sleep.
If it’s ~4Hz - see Yuta Senzai’s visual cortex paper.
@Vitor yes, Long-Evans, but no these signals are not inverted (it’s from tetrodes so extracellular recordings though). The putative spike waveforms are inverted but that is not what is shown here… this is the raw, unfiltered, unreferenced signal from each channel.
Do you know what it is?!👀
@elduvelle I asked about the signals being inverted because I've seen a few labs that like to see LFP/wideband inverted for some reason ( one justification I've heard was to have spikes going up ).
This reminds me a bit the so called mu rhythm which can be very prominent in long evans rats but looks upside down to me. I'm not sure this is it but the waveforms looks like it, although it's hard to judge subjectively from a plot layout I'm not familiar with. Also the distance between the troughs (peaks in your case) would be around 100ms which seems what you have there. It is also stronger in the cortex above the hippocampus.
Mu rhythm as defined here has nothing to do with the EEG mu rhythm btw.
@Vitor oh yes, the inversion question definitely makes sense, and for example Neuralynx systems invert by default.
Interesting…
Do you have a favourite reference paper for that mu rhythm? I found this one and it’s very informative but I’m not sure it is the same thing; my rat is definitely whisking at least some of the times when this happens, but it doesn’t look exactly the same and as you say it seems inverted compared to what the paper shows (see their figure below). But maybe (probably) it just looks different depending on where the electrodes are…
@elduvelle I don't have a preferred reference. Im no expert in this rhythm but I happened to work with long Evans ~10 years ago and I remember this damn rhythm (it contaminates the theta detection).
Ive never seen a phase reversal of that rhythm but again I'm no expert.
Does it come and go, or is it very constant? I remember some rats had this more frequently than others.
@Vitor it definitely comes and goes… let me know if you see this example video. The rat wasn’t really moving during the entire video (but wasn’t asleep either). I also do not remember seeing this that strongly in other rats but I don’t often implant that high above hippocampus.
@elduvelle it really looks like an inverted mu. Also this dynamics of coming and going. Also I had this was the rats were immobile.
Are you moving the tetrodes? Maybe eventually you'll see a reversal. Let me know I'm curious
@dlevenstein@Vitor … I usually put my ground screw at the back but this time I put it at the front so potentially above frontal cortex (?) - grounds screws should not influence the signals like this right? But.. could it be that? It would explained the reversed aspect…
@elduvelle@dlevenstein I think HVS and mu are the same thing. Probably HVS is a better term in fact as I don't really believe it is analogous to the my rhythm classically defined in human EEG. 4 Hz I think it's something else entirely unless I'm missing something.
@elduvelle@dlevenstein it's hard to be 100% sure but intuitively I'd say with relative confidence that changing the ground location as you described wouldn't change the polarity of that rhythm
@elduvelle@dlevenstein usually the ground screws are very wide compared to the tetrodes. This averages the signal across a much bigger area and tends to dilute brain signals up the point we can't see them as clearly as that. This is my intuition at least, hopefully it's not totally wrong. They are also not really entering the brain I suppose? So they pick lot of things "floating" in the CSF? Id think it's extremely unlikely you would see a signal as clear as that using a ground screw.
But the contradictory bit is that this seems to be ~4-5 Hz. And I don't think this was in the visual cortex. At least I was trying to target hippocampus CA1 😅 and I am pretty sure it was because when these signals went away, I would see the SPW-Rs and theta but the ripples were also weird iirc ..
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