I'm able to calculate the slope easily by placing the cursors over the linear portion. However, often the stats list the rise-slope as "not found". Is there a certain way I need to align the cursors in order to calculate the rise-slope?
Thanks,
Tom
Hi,
Maybe some of your fPSPs fall out from your cursor settings because they occur a bit later or is artifactual. I would reccomend to reject those if they are just a few. You may check how looks the 'not-found' fEPSP in your recording.
Hope it helped!
Thanks for your response, Marcel. I actually get a "not found" when I'm analyzing a single sweep with the cursors on the linear portion of the fEPSP. Often if I do the stats on a set of sweeps I get a single rise-slope value that is the same across all the sweeps, even for example with my input/output data.
Hi Thomas,
I think Jorge has a point, if the cursors are placed close together, there will be too few points for clampfit to calculate the slope. As stated above, if these are a few traces only, you can discard them, but if this happens often enough, you can do the following trick to be able to use these data: in "clamplfit 10' click on the anaylysis tab, in the fifth or sixth section you will find an "interpolation" function; use this function to increase the number of points the program will be able to detect. What this thing is actually doing is dividing the acquisition time by a factor that you determine (or in other words, it is a virtual 'increase' of the acquisition frequency). This way the program artificially creates as many points as determined by the factor you chose. That is, if you use a factor of 2, there will be twice as much points for clampfit to use for its calculations. Importantly, this is not altering your trace because the amplitude of the new points will fall within the original trace. For future recordings, it may be more efficient to just increase the acquisition frequency from, say 1 khz (1 ms window) to 5kHz (0.2 ms window).
FYI, within this same group, there is another function called "Data Reduction" that does exactly the opposite. This function can come helpful if you want to coanalyze traces that have different acquisition settings. However, be aware that data reduction can alter your trace because has a filtering-like effect. Also, if the number of points to calculate the slope is not the problem, data reduction could be helpful exactly because what I just mentioned (the filtering-like effect). Another reason clampfit may not find a slope is because the signal to noise ratio is bad, too much noise, especially when signals are small. The filtering effec of data reduction could smoothen your trace so clampfit may find a slope.
Good Luck!!
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