Coherence NxN configuration

[Raymundo.Cassani]

@Marcos

Should I select the "Save individual results..." option, which will generate multiple files to later calculate the average, or the "Average cross-spectra..." option, which will generate a single file?

1. "Save individual results..." This option will compute one estimation of MSC for each epoch, using the data only for that epoch, using N windows (N depend on the window length and percentage of overlap). This option can be used to evaluate any change in coherence across epochs.

2. "Average cross-spectra..." This option will compute one estimation of MSC for all the epochs, using the data from all the epochs, using N windows × number-of-epochs, thus it is a better estimation of MSC.

The average of MSC results from Option1 are not the same as the MSC obtained with Option 2 as MSC is not linear.

@Marcos

Another point, is it possible to calculate the average coherence values for a frequency range? For example, Theta (4 - 7Hz)... When exporting the file, it asks me to choose a specific frequency (e.g., 5.08Hz). Is it possible to obtain average values for the entire range?

The Coherence NxN [2021] processes uses the Fourier transform to compute the PSD and cross-spectrum, to later compute MSC. Thus, MSC has the same resolution than FT. To obtain MSC in a band range, a different approach can be take, by filtering data and using Hilbert transform to compute the T-F representation and compute the PSD and cross-spectrum from that T-F representation. More information on these differences here: Lagged coherence - #3 by Raymundo.Cassani

In a not-too-far update, the coherence process GUI will be updated to include both (Fourier transform and Hilbert (or wavelet) transform) approaches

@Marcos

Is it possible to obtain average values for the entire range?

Yes, with the process Frequency > Group in time or frequency bands