In my LTD experiments, I set the baseline to 60-70% of maximal response. However when I perform the baseline stimulation, the response don't usually reach the previous slope determined as 60-70% of maximal response. So, must I change my stimulation voltage or I must consider my maximal response could have changed in the same way than my 60-70% response?
Thanking any answer.
Ideally you would set your stimulation intensity to elicit a typical amplitude size and observe if the amplitude size is stable for several minutes (I used to wait until my recording is stable for 10 minutes). You can then go ahead to do an input/output curve, determine the maximal response and calculate the 60% maximal response. Then you can start your LTD experiment by recording the baseline.
Dear Claudia,
Thanks for the answer given. In my experiments I perform a similar process to the one you describe. However, in some cases, the baseline established didn't reach the 60% maximal response inferred from I/O curve. In your experiments, do you obtain the 60% maximal response in the baseline?
Doing an I/O curve can induce by itself a slight potentiation of fEPSPs and in certain situations can damage afferents at maximal voltage/current levels, especially in the current stimulation mode. The first case causes a wrong estimation of the 60% and might be avoidable by using only few stimulation at greater intervals and the second case, will just lead to smaller fEPSP during baseline stimulation. Thus, avoiding stimulation at the maximum, or just doing it once, might be better. The 60-70% for LTD induction might be too high and can induce damage of afferents and subsequently get a nice “LTD”, thus the fiber volley responses needs to be analyzed and compared with before and after LTD induction, and stimulation voltage could be around 2V. Best. T
Thank you so much for your answer Mr. Behnisch. I know about the possibility of potentiation induced by a short interstimulus interval. However, I think this is not my case, because I use 1 minute between each stimulation and it usually works fine. Maybe, I can be suffering the other explanation given by you. For stimulation I use voltage, not current, to avoid damage of the electrodes and in a range between 750 and 3000 mV. I usually stop the IO curve when it reaches a plateau, but it could be too late and it is possible to have damage of afferents fibers as you say. What I observed in many cases is something like a death rattle, because the response increase and when it reaches a maximum it starts to decrease and finally disappears in few minutes. It happens during IO curve or when I have set the baseline. Sometimes response doesn't disappear and just has a lower slope than the expected but it could be due to the same. I will take care with maximal response next time. Thanks again and I would be grateful for any other suggestion about this topic.
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