[Eeglablist] What is the best approach to reject bad components when using a 256-channel (EGI) equipment

[anoop jagadeesh]

Dear all,

We use a 256-channel EGI equipment to measure auditory evoked potentials.
There are a few questions I have and I hope you can answer them for me

1. Should I run the ICA for the full 256 channels or using a PCA (as
suggested in Makoto's preprocessing pipeline)? Till now I have done it
using the PCA approach. But it would be helpful to know of any other
approaches to handle the high-density recordings.

2. Even after running the ICA (RUNICA) with a PCA value of 64, there are
many components which are very difficult to explain. Normally, we would
remove only the components which are"outside the head". However, there are
many components which are clearly 'bad' inside the head. Especially, there
are components within the 64 which look like a localised dot. Do we remove
these components? Please note that I have seen instances where there are 10
(out of 64) or even more such dot components

3. Another important issue I have encountered is there are many cases where
'spindles' (very likely related to sleep) occur. These spindles are often
seen in the top 5 most robust components. Do we keep them or remove them?

Simply put, how strict do we need to be while rejecting the bad components.
Inputs regarding this are highly appreciated

Regards

-- 
Anoop B J
Junior Research Fellow
Dept of Audiology,
All India Institute of Speech and Hearing, Mysuru, India
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