[Eeglablist] Plotting 3D voltage topography at single time point

Stefon van Noordt stefonv0 at gmail.com
Wed Mar 3 07:10:30 PST 2021


Dear Kaelasha,

Perhaps not the most elegant solution, but you could manually change the
data in the EEG structure so that it reflects the voltages at a specific
time point for each channel. Then you could pass this to the pop_headplot
function.

% Pull out the voltage values at the time point of interest for each
channel (where the time point in this example is 1000)
my_spike_dat = EEG.data(:,1000);

% Load dataset from the same study, then epoch the data to any event (it
doesn't matter which one as you'll be replacing the data)

% Reduce down to only 2 epochs (as you said, the topo functions typically
require epoched data)
EEG = pop_select( EEG,'trial',[1 2] );

% Replace data at each time point with your spike EEG data
for i = 1:1343;
    EEG.data(:,i,1) = my_spike_dat;
    EEG.data(:,i,2) = my_spike_dat;
end

% Now you have 2 epochs, were every time point is the same data for each
channel

% Use pop_headplot to plot 3D map (it doesn't matter which time point you
choose, so 100 in the example below is arbitrary)
figure; EEG = pop_headplot(EEG, 1, 100,...
    'eeg topo', [1  1],...
    'setup',...
    {'/media/spline_for_headplot.spl' 'meshfile' 'mheadnew.mat' 'transform'
[0 -24 -48 -0.05 0 -1.57 1080 1140 1110] },...
    'maplimits',[-1,4],'electrodes','off');

You'll likely want to create your own mesh file and change the values here
for the transform based on your montage.

Hopefully this will be useful.

Best,
Stefon



On Tue, Mar 2, 2021 at 7:39 PM Clement Lee <cll008 at eng.ucsd.edu> wrote:

> Hi Kaelasha,
>
> I don't think EEGLAB has a specific function for plotting 3D topographies
> for data from a single time point. However, the function used to plot the
> 3D ERP map series is `pop_headplot.m` You may be able to hack it to
> accomplish what you want.
>
> Best,
> Clement Lee
> Applications Programmer
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, UC San Diego
> 858-822-7535
>
>
> On Tue, Mar 2, 2021 at 8:20 AM Kaelasha Tyler <kaelasha.tyler at gmail.com>
> wrote:
>
> > Hi all,
> >
> > How do you plot a 3D voltage topography at a single time point in
> > continuous data?
> >
> > ****
> > I am familiar with plotting 3D topographies with epoched data. Eg:
> > Plot> ERP map series> In 3D
> >
> > However in my present case, I am wanting to plot in 3D the voltage
> > topography at the peak of a single seizure spike and wave. In this case,
> > there is no epoched data, continuous only. Also, I am not wanting to plot
> > an average of a whole epoch, but just the time point at the peak of the
> > spike and wave.
> >
> > If anyone can help me with this, that would be greatly appreciated.
> >
> > Regards,
> > Kaelasha
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