[Eeglablist] Removing 1/f in spectopo() before plotting topography at select frequencies.

[Brian Harvey]

Thanks for your response Arno,

For the case where I would like to visualize amplitude topographies at a particular frequency when there are discrete peaks, I can do this manually outside of EEG lab functions (convert to relative measures, i.e. divide by total power). I just wanted to see if there was an option that I was overlooking in spectopo() or any related EEGLAB functions

Cheers,
Brian


-----Original Message-----
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Delorme, Arnaud
Sent: Monday, November 18, 2019 10:41 AM
Cc: eeglablist at sccn.ucsd.edu
Subject: Re: [Eeglablist] Removing 1/f in spectopo() before plotting topography at select frequencies.

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Dear Brian,



When you compare conditions at the study level in EEGLAB, there is a checkbox (in the spectrum plotting options) that allows you to remove common spectral activity between conditions at the subject level (this will effectively remove the 1/f trend and in fact any activity in the spectrum that is common to the different conditions).



Best wishes,



Arno



> On Nov 15, 2019, at 8:48 PM, Brian Harvey <brian.harvey at biogen.com> wrote:

> 

> Has an option been implemented in spectopo() or similar functions that can correct the PSD's for the underlying 1/f? Often times I am finding that scalp topographies are representing the power by absolute magnitude but not accounting for the signal-to-noise at any particular frequency.

> 

> For example, would a channels that has a larger power at 40Hz but no peak at 40Hz be more representative of brain activation vs. a channel that has a distinct peak at 40Hz but the peak power is lower than that of the former?

> 

> I appreciate your inpute.

> 

> Brian Harvey

> Biogen

> 

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