[Eeglablist] Combining data from different tasks within the same EEG session for ICA

[Makoto Miyakoshi]

Dear Neil,

> Does anyone have a good sense on whether it would be valid to combine
epochs from the same EEG session, but different tasks in order to maximise
data for ICA decomposition?

Yes, it is valid. Of course the cost is that you may lose ICA's sensitivity
to each of the task.

> similar artifacts to be removed (eye movement, muscle, line noise).

Yes. In addition, cognition-common brain mechanisms as well (attention,
alertness, etc)

> However, the underlying neural activity will differ between the tasks
(for example the Sternberg working memory task generates a large amount of
posterior alpha, while the Go/Nogo task does not, but does generate a large
N2 and P3 component).

As long as each of the task design is established and sensitive to evoke
ERP, it should be fine.

Before wondering, you can try
1. separate data into subsets with different tasks and run ICA on each
2. run ICA on task-concatenated data
and compare results to evaluate the trade off (it will be confusing and
hard though)

Makoto

On Thu, May 28, 2015 at 8:43 PM, Neil Bailey <neil.bailey at monash.edu> wrote:

> Hi all
>
> Does anyone have a good sense on whether it would be valid to combine
> epochs from the same EEG session, but different tasks in order to maximise
> data for ICA decomposition?
>
> I'm aware that feeding more data into the ICA gets better results, and the
> data from the different tasks will have similar artifacts to be removed
> (eye movement, muscle, line noise). However, the underlying neural activity
> will differ between the tasks (for example the Sternberg working memory
> task generates a large amount of posterior alpha, while the Go/Nogo task
> does not, but does generate a large N2 and P3 component).
>
> Will the differences in the underlying neural activity between tasks
> negatively affect the results of the ICA if activity from different tasks
> is combined? And will it matter if the epochs from different tasks are of
> different lengths?
>
> Kind regards,
>
> --
> Neil Bailey (PhD)
> Monash Alfred Psychiatry Research Centre
> Neil.Bailey at Monash.edu
> (03) 9076 5032
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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