[Eeglablist] Freq power baseline question

David Ryan ryand1 at goldmail.etsu.edu
Mon Nov 4 12:04:27 PST 2019


Scott Makeig,
Thank you for your reply. I am familiar with ERSPs; however, my study
has correct and incorrect responses in different conditions and
results in single trial responses (e.g., 20 dB SNR condition 1
incorrect response from several participants). I was unable to use
this function as EEGLAB STUDY views single trials as continuous EEG,
not a single epoch, and the newtimef() throws an error for continuous
data.  This limitation led me to using Spectopo.
Could I baseline correct the Spectopo output by epoching prior to the
stimulus, using Spectopo to find frequency power, then subtract from
the frequency power
epoched post stimulus? Is a simple subtraction of power from pre and
post stimulus appropriate?

Thanks,
Dave

On Sat, Nov 2, 2019 at 5:01 PM Scott Makeig <smakeig at ucsd.edu> wrote:
>
> Dave -  Your msg has indeed appeared on the eeglablist 4 times... Spectopo does not subtract a (log) baseline. The function newtimef() computes event-related spectral perturbations (ERSPs).
>
> Scott Makeig
>
> On Tue, Oct 29, 2019 at 12:41 PM David Ryan <ryand1 at goldmail.etsu.edu> wrote:
>>
>> Hello,
>> I have sent this email to the listserv several times, gotten a
>> confirmation email but never saw it in the listserv. Do I need to
>> correct something?
>>
>> Thanks,
>> Dave
>>
>>
>> Hello,
>>
>> I am looking into frequency power changes with the onset of an
>> auditory stimulus and a time window of 0-700ms utilizing the script
>> below. Does this process baseline correct? Does it need a baseline
>> correction?
>>
>> [spectra,freqs] = spectopo (EEG.data(Fz,:,:), 0, EEG.srate);
>>
>> %Data ranges
>> hz8 = find(freqs>7 & freqs<9);
>> hz7 = find(freqs>6 & freqs<8);
>> hz6 = find(freqs>5 & freqs<7);
>> hz5 = find(freqs>4 & freqs<6);
>> hz4 = find(freqs>3 & freqs<5);
>>
>>
>> % Compute Power
>> hz8powerFz = 10^(mean(spectra(hz8))/10);
>> hz7powerFz = 10^(mean(spectra(hz7))/10);
>> hz6powerFz = 10^(mean(spectra(hz6))/10);
>> hz5powerFz = 10^(mean(spectra(hz5))/10);
>> hz4powerFz = 10^(mean(spectra(hz4))/10);
>>
>>
>> Thanks,
>> Dave
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>
>
>
> --
> Scott Makeig, Research Scientist and Director, Swartz Center for Computational Neuroscience, Institute for Neural Computation, University of California San Diego, La Jolla CA 92093-0961, http://sccn.ucsd.edu/~scott


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