Extracting spectral values from Scouts

Discussions
1

Hi everyone,

I have source localised individual trial data for some subjects. Within each subject, I have sorted their trials according to individual stimulus condition. I want to perform some additional analysis in Matlab on single trial data. For each of the trials I want to extract averaged delta and theta band responses for a given time period from two ROIs/scouts. This is where I am getting stuck.

Here are the steps that I have undertaken so far

  • Project the individual trials to MNI space
  • Perform spatial smoothing

Now from this data I want to extract values from two scouts (DK atlas).
Here are my steps:

  • I perform a Hilbert transform (Frequency > Hilbert Transform > select the two scouts > "Edit" > Specify delta and theta bands).
  • Extract Values > Specify time window > Specify frequency range
    Now at this stage, I can either add 0-4Hz or 4-8Hz or 0-8Hz. But not 0-4Hz AND 4-8Hz.
    If I select 0-8Hz then this averages the values across the entire delta-theta spectrum.

I was wondering if it is possible to extract the two values per trial in one single run or will I have to run this process twice (once for delta band, once for theta band)?

Thanks!

2

At this point, the content of the Hilbert transform file, it has a TF of the shape [nScouts, nTimeSamples, nBands].

Do you want to average the power values from the Hilbert transform for the given Time window?
If this is the case, you can use instead the process Average > Average time, this will be performed for each band, thus the result will have the shape [nScouts, 2, nBands].

  • Where [nScouts, 1, nBands] == [nScouts, 2, nBands] and contain the time average of the HT for a given Scout and Band
3

Thanks for the quick reply. This is super useful.

A follow up question on that -
As I am dealing with individual trial data per participant, after the average time window step, what's the best way to extract these values in one single data structure?
I tried it with "Extract Values" and only ticking the "Match signals between files using their names". However, this results in a data structure with these dimensions ->
2 x <n> x 2 (n= number of trials)
where each value is repeating twice?