Peak to peak ERP amplitude

Hello,

I want to extract my peaks (P50 and N90) and/or my peak to peak (p50 to n90) ERP amplitude, for now I have tried:

  • to select my time-window: I have the latencies and a min and max but I do not know the units is it Volts or no units as it is written on the graph ?
  • to extract>find maximum in time fo a time window around my peak: it is running but then I have a graph with straigh lines but no numerical values..? I am sure I am missing something easy but I do not know what

Can you help me please :slight_smile:
Thank you,
marie

1 Like

I think a peak to peak measure in BS would be very useful! :slight_smile:

The same units should be displayed at the bottom of the figure when you have a time window selected, and at the top-right corner (column view) or left side (butterfly view) of the figure. If this is not the case, there is something wrong with your data import.
All the values are save international units in the files of the Brainstorm database. For EEG, this means that the values saved in the imported data files should be in the range of 10^-6 (microVolts) to 10^-3 (milliVolt), and displayed as microVolts.

Example of the EEG/Epilepsy tutorial: https://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy

image

Right-click > File > Export to Matlab > "DataMat":

Data exported as "DataMat"
>> Fmin = min(DataMat.F(:))
Fmin =
  -2.7289e-04
>> Fmax = max(DataMat.F(:))
Fmax =
   1.0945e-04

If you see "No units" anywhere when displaying EEG data that haven't been normalized, you should fix your import procedures before moving forward, as all the units will be wrong.

to extract>find maximum in time fo a time window around my peak: it is running but then I have a graph with straigh lines but no numerical values..?

These straight lines ARE your maximal values. As you have only one per sensor, these appear as flat.
To do something with these values, you need to process them manually with Matlab.

To get started with Brainstorm scripting, read this tutorial:
https://neuroimage.usc.edu/brainstorm/Tutorials/Scripting

Hey François,

Thank you for your answer this is better now :slight_smile: