Stimulus artifact

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rkesarwa
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Stimulus artifact

Hi

I do extracellular field recordings to study LTP and LTD. I find that the peak of my stimulus artefact runs with the fEPSP slope. ie. if the fEPSP slope increases, the artefact for that recording also increases. It seems that for many of my LTD recordings, a decrease in artefact peak runs with the observed decrease in fEPSP slope after conditioning.

Is this something to be concerned about? Is the observed decrease in fEPSP due to actual LTD-induction or is it due to some malfunction in my stimulating electrode that makes it draw less current after the conditioning phase?

I have attached an example of how the artefact peak changes over time. The first 20 minutes is the baseline period (0.05Hz), followed by 2 minutes of 5Hz stimulation, and then another hour of post-conditioning recording at 0.05Hz. Plotting the fEPSP slope gives a very similar trace.

Rohit

The FFM
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ok this is second hand

ok this is second hand information after I consulted with a former colleague, but I hope it might help

One possible thing you can do is to measure the amplitude of the presynaptic volley.  It is the small blip before the field EPSP.  

You should check whether that also changes in amplitude with the change in stimulus artefact.  If the presynaptic volley does not change in amplitude then I think you are safe

Good luck