Colorado State University - Pueblo
Question
Asked 21st Jul, 2014
What is the best way to measure the rising slope of an EPSP in the dentate gyrus?
I'm in trouble with the rising slope measurements of EPSP in the denta gyrus. I'm inducing LTP in this region and to reveal the increase of synaptic strenght I'm performing an off-line analysis using p-clamp, and I don't know if I should I take count of the late phase of the peak (Half-width) like in figure b or I should place the analyzing axes like in fig. a. Thanks
Most recent answer
If we can continue on that line of thought why are not people using maximum rate of raise more often, it stands to reason that it would be less sensitive to cursor placement! I worked with action potentials a long time and dV/dt max is an accepted analysis approach there. just finished analyzing a bunch of data in CA1 and still struggle with how best to interpret the I/O data in terms of fiber volley fEPSP relationship
Popular answers (1)
Stanford University
The earlier in the rising phase you can get, the better. You need to avoid measuring the fiber volley, so generally start at the earliest point where the rising phase becomes linear after the FV. Rarely go past about 50-60%, and certainly not where the rising phase begins leveling off. The population spike is lurking in there whether you can see it or not, so the earlier in the rising phase you can terminate your measurement (consistent with getting an accurate and reproducible measurement) the better. I would have measured yours more like this:
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All Answers (7)
University of Kentucky
I would not place cursors in A or B positions (as provided in your examples).
You don't want to be close to the bottom as the slope is almost zero and that would mess up your measurements. Also, as you know, after LTP the peak moves left, so be careful that both cursors are always on the descending slope of the EPSP, not too much at the top, not too much at the bottom. In A, the first cursor is too much at the top. in B the second cursor is too much at the bottom.
We verify every measure on every EPSP to make sure both cursors are on the linear portion of the descending slope.
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Südharz Klinikum Nordhausen gGmbH
I have been comparing integrity of slope-evaluation methods for a long time (methods paper on the way). your case is easy because you lack fPopS contamination.
Method 1: measure the slope between 10-40% or 10-80% of your amplitude, so you get rid of the fiber volley
Method 2: extract the first derivative and therefore the maximum slope
Method 3: calculate the AUC of the trace
plot both of them against stimulation intensity and check what seems more realistic for your dataset.
Cheers from Germany!
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Dartmouth–Hitchcock Medical Center
I have also used clampex to do my off-line analyses for fEPSPs and I agree with the above comments. In your first example (a), move the cursor 1 forward to that it is not on the peak or approximately 10% of the amplitude as Ismini mentioned. Then, move through all of the sweeps to make sure that at no point either cursor have traces that are contaminated by falling outside the initial slope. After you tell clampex to calculate the slope, make sure that none of the calculated slopes once converted to percentage of the baseline slope are not some insane values like 300%.
Dartmouth–Hitchcock Medical Center
Also, @Ismini, I look forward to your paper! Let me know on here when it's published.
Stanford University
The earlier in the rising phase you can get, the better. You need to avoid measuring the fiber volley, so generally start at the earliest point where the rising phase becomes linear after the FV. Rarely go past about 50-60%, and certainly not where the rising phase begins leveling off. The population spike is lurking in there whether you can see it or not, so the earlier in the rising phase you can terminate your measurement (consistent with getting an accurate and reproducible measurement) the better. I would have measured yours more like this:
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Colorado State University - Pueblo
If we can continue on that line of thought why are not people using maximum rate of raise more often, it stands to reason that it would be less sensitive to cursor placement! I worked with action potentials a long time and dV/dt max is an accepted analysis approach there. just finished analyzing a bunch of data in CA1 and still struggle with how best to interpret the I/O data in terms of fiber volley fEPSP relationship
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