ABR Peaks Positive or Negative

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NVanderStoep
Posts: 5
Joined: Fri Apr 13, 2018 10:56 am

ABR Peaks Positive or Negative

Post by NVanderStoep » Mon Oct 01, 2018 11:01 am

Dear Coen,

we are measuring ABRs in our lab with BioSemi ABR electrodes. We finally have pretty clean ABR measurements. However, now that we are analysing data from a study, I am doubting whether we are labeling the peak in the right way. The wave V latency is quite early with 90dB clicks if we interpret the positive peaks as wave I-VII. The click has a fixed delay of 1 ms after trigger onset, so wave V should be around 6 ms with normal hearing. Inverting the y-axis seems to give more plausible latencies, but from what I get from the forum and the website, the ABR peaks really are the positive peaks. I have attached two graphs, it's the same ABR (binaural presentation, 90 dB, 0 ILD, 0 ITD, LA and RA on mastoid, references on central forehead, CMS and DRL centered around ABR reference electrode (to the left and right on forehead)), but one plotted with negative up, and one with negative down. Could you help out with figuring out which direction is which?

Best,
Nathan

Positive up:
Screenshot 2018-10-01 at 11.50.04.png
Screenshot 2018-10-01 at 11.50.04.png (21.66 KiB) Viewed 1896 times
Negative up:
Screenshot 2018-10-01 at 11.50.58.png
Screenshot 2018-10-01 at 11.50.58.png (22.08 KiB) Viewed 1896 times

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