[Eeglablist] Topographical plots for frequency band

[Nicolas LEBAR]

Hi Rohit and Makoto,

Thanks for your comments!

For now, the only way I found (in theory, I have to try it) to get a topographical plot for a frequency band (let's say alpha 8-12Hz) is to run the pop_newtimef() function and then extract my frequencies of interest from the matrices and to average it for each time point, and to do so with all my 64 channels. Then, plot the values using pop_spectopo() function. I m still wondering if it's correct or if there is an easiest way?

Regards,
Nico

"Dr.Rohit Tyagi" <rohittyagi_2k at rediffmail.com> wrote:Thanks Makoto for your inputs.

Regards,
Rohit

From: Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
Sent: Fri, 26 Dec 2014 08:42:18 
To: "Dr.Rohit Tyagi" <rohittyagi_2k at rediffmail.com>
Cc: eeglablist <eeglablist at sccn.ucsd.edu>, Yamil Vidal Dos Santos <hvidaldossantos at gmail.com>, Nicolas LEBAR <nicolas.lebar at etu.univ-amu.fr>
Subject: Re: [Eeglablist] Topographical plots for frequency band
Dear Rohit,
> is it possible to give a frequency band - say Alpha as average of all frequencies from 8-12Hz ?

Unfortunately I don';t think GUI supports it unless you read so in the help.
> But from what Nico said - it seems he wants to plot this information "at a specific time point".
Band-pass filter, Hilbert transform, and use pop_spectopo() function.
> As far as I know, the frequency domain / power spectral density plot as made by spectopo should give this information about a specific time interval of data - say 1 second/ 10 seconds etc. I don';t think it can be for a particular time point.
Yes.
> There might be ways to make this time segment shorter, but that would probably be detrimental to the depiction of slower waveforms.

You can';t cheat the time-frequency trade off.
> On the other hand, I wonder whether Wavelet based methods will be more appropriate for shorter time segments ?

I would use the abovementioned method using Hilbert transform since it gives you instantaneous amplitude.
Makoto
On Fri, Dec 19, 2014 at 12:10 AM, Dr.Rohit Tyagi <rohittyagi_2k at rediffmail.com> wrote:
Hi Nico and Yamil,

In addition to Nicolas'; question and Yamil';s suggestion, I also wanted to know a way to make topographical plots for particular frequency bands. like when using pop_spectopo, instead of giving particular frequency values (like default 6, 11 and 22) is it possible to give a frequency band - say Alpha as average of all frequencies from 8-12Hz ?

But from what Nico said - it seems he wants to plot this information "at a specific time point".
As far as I know, the frequency domain / power spectral density plot as made by spectopo should give this information about a specific time interval of data - say 1 second/ 10 seconds etc. I don';t think it can be for a particular time point. There might be ways to make this time segment shorter, but that would probably be detrimental to the depiction of slower waveforms.
On the other hand, I wonder whether Wavelet based methods will be more appropriate for shorter time segments ?

Regards,
Rohit

From: Yamil Vidal Dos Santos <hvidaldossantos at gmail.com>
Sent: Tue, 09 Dec 2014 11:24:48 
To: Nicolas LEBAR <nicolas.lebar at etu.univ-amu.fr>
Cc: eeglablist <eeglablist at sccn.ucsd.edu>
Subject: Re: [Eeglablist] Topographical plots for frequency band
Hi Nicolas,
The simplest would be to band pass filter the data to your freq range of interest and then you can simply use topoplot.m
As you would be using a rather narrow filter, I recommend you to read this article in order to design a filter that won';;t mess up your data.
http://www.sciencedirect.com/science/article/pii/S0165027014002866

I cannot think of another option, but I';;m interested in the opinion of the community.
Best,
Yamil

On Fri, Dec 5, 2014 at 5:57 PM, Nicolas LEBAR <nicolas.lebar at etu.univ-amu.fr> wrote:
Hi all!

I';;m looking for a way to plot a frequency-band activity (let';;s say average alpha 8-12Hz) for 64 electrodes into a topographical map for each subjects (and eventually on a subject average) at a specific time point. The next step is then to have several of these maps for several chronologically different time point. Is there any option to do this, or a direction I can follow to make a script?

Thanks a lot for anything that helps.

Nico
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Makoto Miyakoshi
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Institute for Neural Computation, University of California San Diego

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