[Eeglablist] ICA with 128 channels

[Scott Makeig]

Maria - The first question is how much data you are decomposing... e.g. With
4x the number of channels, you should use > 16x the data length in the
decomposition... For 128 channels, you should use >>128^2*20 (320k) time
points. At 250 Hz sampling rate, that would be at least 15 min or more of
continuous data or data epochs... One might say (poetically) that the
sources need this much data to express their independence...

Scott Makeig

On Sun, Jul 27, 2008 at 6:35 PM, <mjalbrzikowski8 at ucla.edu> wrote:

> Hi,
>   I am currently running ICA through data that was collected with a 128
> channel cap.  However, unlike the data that I have previously worked with
> less channels, ICA does not return identifiable blink (VEOG or HEOG)
> components with this electrode setup. I'm thinking this is because after you
> ICA, you get 128 components, and VEOG or HEOG is dispersed across several
> different components.  However, I cannot accurately identify these
> components now.  It was muich easier to pull out blink components with less
> channels.  Has anyone else had this problem?  If so, did you figure out any
> solutions that you would like to share?
> Thank-you,
> Maria Jalbrzikowski
>



-- 
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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