[Eeglablist] [How to] Phase synchronization and Filter type

[Stanley Klein]

Arno, you say the number of cycles of EEG gamma is between 6 and 12. But
what about the recent Yuval-Greenberg article in Neuron pointing out that
the kind of gamma often found in EEG has a much broader bandwidth (much
fewer cycles) and is very tightly connected to an artifact of microsaccades
after filtering the EEG. In a previous posting to eeglablist I had mentioned
the poster by that group at the recent Cognitive Neuroscience meeting in San
Francisco. Their article is now published at:
Neuron, Vol 58, 429-441, 08 May 2008
Transient Induced Gamma-Band Response in EEG as a Manifestation of Miniature
Saccades
Shlomit Yuval-Greenberg, Orr Tomer, Alon S. Keren,Israel
Nelken,<http://www.neuron.org/content/article/abstract?uid=PIIS0896627308003012#aff2>and
Leon Y. Deouell
<http://www.neuron.org/content/article/abstract?uid=PIIS0896627308003012#aff1>
I look forward to an interesting discussion on the topic. They are clear
that their conclusion is specifically for EEG, not to evidence of gamma in
ECoG or microelectrode studies.

Lee, regarding your low pass filtering question, I'm of late really liking
the Hanning filter because of its simplicity. As I recall, in the Fourier
domain it is simply one cycle of (1+cos(pi f/f0)). And it is reasonably well
behaved in time.
Stan

On Fri, Jun 13, 2008 at 1:46 AM, arno delorme <arno at ucsd.edu> wrote:

> Dear Lee,
> according to the literature, standard values for the number of cycles at
> gamma (30-150Hz) are from 6 to 12.
> Prior filtering (unless you are using a hilbert transform) is
> probably unnecessary.
> To reduce noise you may also want to use the multitaper option which is
> available from the command line in the timef() function.
>
> Best regards,
>
> Arno
>
> On 8 juin 08, at 09:57, TH Lee wrote:
>
> Dear Collegues
>
> These days, I've tried to analyze the Phase synchronization of my EEG data
> (1000Hz sampling rate).
> Especially, i concered about Gamma band synchronization.
> For choosing optimal parametic value, i've read almost references in
> relation to this issue.
> But still i can't find the optimal parametic value to analyze the data.
> Because, according to aurthor, they aplied filter type differently.
> For instance, some aurthor used Kaiser type FIR filter for filtering.
> However, the other used Hannning type FIR window.
> So i can't decide the analyzing procedure.
>
> Please let me know the best parametical choice for analyzing in EEGLAB
> (e.g., Filter Type, Sampling rate, window length. etc)
> Thanks
>
>
> Lee
>
>
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