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.