[Eeglablist] ICA assumption (independence of sources)

ali zahedi ali.zahedi.bham at gmail.com
Fri Jan 27 17:10:26 PST 2017

Dear Makoto,

Thank you for your reply.
I am sorry I am little bit confused...
Do you mean that: when we record an EEG, with for example visual
stimulation and apply ICA to EEG, we get a number of sources each
corresponds to a physiological activity. For example, we could get sources
correspond to eye movement, muscle activity, visual task, heart beat and
etc. The brain sources are not independent in reality but because the
physiological activities are independent (e.g. eye movement, muscle
activity, visual task, heart beat and etc), then we could say ICA
assumption can work for EEG. And in this case, we are not talking about the
brain sources of each physiological activity, we only consider each
physiological activity as an independent source that could be estimated by
Did I understand correctly?

Kindest regards,

On Thu, Jan 26, 2017 at 9:34 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu>

> Dear Ali,
> > the brain sources are not independent in reality,
> That may be true. In that case, ICA is extracting independent part of
> brain activity.
> However, at least in a standard psychological assumptions, when you are
> performing visual task, your auditory cortex is not directly engaged,
> therefore EEG from the visual cortex and the auditory cortex should be
> independent. Don't you agree?
> Makoto
> On Tue, Jan 24, 2017 at 5:30 AM, ali zahedi <ali.zahedi.bham at gmail.com>
> wrote:
>> Hi all,
>> I have a question about one of the assumptions of the ICA on estimated
>> sources; "the sources estimated by ICA are statistically independent". If
>> we want to apply ICA to EEG data, does this assumption make sense for brain
>> sources? the brain sources are not independent in reality, so how does ICA
>> work for EEG data?
>> Thank you in advance,
>> Ali
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> --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
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