[Eeglablist] Does pop_clean_rawdata depend on the type of high-pass filt (0.1 or 1 Hz)?

Bianca Monachesi bianca.monachesi at unitn.it
Tue Jul 27 03:59:19 PDT 2021


Hi Velu,

Thank you very much for your help. The command line works perfectly ;-)

Best,

Il giorno mar 27 lug 2021 alle ore 12:01 Velu Prabhakar Kumaravel <
velu.kumaravel at unitn.it> ha scritto:

> Hi Bianca,
>
> I have observed minor differences in the list of bad channels if you use
> the same data consequently. This is because *clean_rawdata *uses a robust
> approach (RANSAC) to compute the Pearson correlation of channels with their
> neighbors and every time you run the algorithm, it might consider a
> different set of samples leading to slightly different resultant
> correlation values (This is rare, though).
>
> Filtering EEG at 1 Hz would reduce much more low-frequency noise peaks
> compared to filtering at 0.1 Hz. This can change the list of bad channels,
> especially for noisier subjects. This is more likely to be true for any
> other bad channel detection method.
>
> Given these, you may
>
> 1) apply 1 Hz filter to the raw data
> 2) detect bad channels using clean_rawdata (store the list of bad channels)
> *         bad_channels = find(EEG.etc.clean_channel_mask == 0); % I used
> this command in the past, please verify if it works*
> 3) perform ICA
>
> 4) apply 0.1 Hz filter to the raw data
> 5) remove *bad_channels *manually computed in step - 2
> 6) transfer ICA weights computed in step - 3
>
>
> Hope this helps.
>
> Best regards,
>
> Velu Prabhakar Kumaravel, Ph.D. Student
> Center for Mind/Brain Sciences,
> University of Trento, Italy
>
>
> On Mon, 26 Jul 2021 at 17:09, Bianca Monachesi via eeglablist <
> eeglablist at sccn.ucsd.edu> wrote:
>
>> Dear EEGlab users,
>>
>> I used "pop_clean_rawdata" to find and remove bad channels (after
>> filtering
>> step) but the number of channels found on a signal high-pass filtered at 1
>> hz is different from the number of channels found on a signal filtered at
>> 0.1 hz. Does it make sense? Which is the relationship between filtering
>> and
>> the function clean_rawdata?
>>
>> This unbalance in the number of channel can be insidious since according
>> to
>> Mokoto's preprocessing pipeline (
>> https://sccn.ucsd.edu/wiki/Makoto%27s_preprocessing_pipeline), the ICA
>> performed on a signal high-pass filtered at 1 Hz  should be attached on a
>> signal high-pass filtered at 0.1 Hz, considering that in both signals the
>> number of channels removed and interpolated is the same...
>>
>> Thank you in advance for any kind of help or explanation of the problem.
>>
>> Best,
>>
>> bm
>>
>>
>>
>> --
>> Bianca Monachesi, PhD
>> Department of Psychology and Cognitive Sciences
>> University of Trento
>> Corso Bettini 31, Rovereto, TN (Italy)
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>

-- 
Bianca Monachesi, PhD
Department of Psychology and Cognitive Sciences
University of Trento
Corso Bettini 31, Rovereto, TN (Italy)


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