After I import the data to EEGLAB do I need to import events and extract epochs before run ICA or after? What will be the difference?
According to the EEGlab FAQ page (http://sccn.ucsd.edu/eeglab/eeglabfaq.html), either way should be fine. I and colleagues in my lab would usually run ICA before extracting epochs, especially if we are interested in removing artifacts such as eyeblinks, which may be quite prevalent in between trials. Also, baseline correction, which is usually performed when data is epoched, changes the relationship between the channels, which could potentially lead ICA to be less successful. On the other hand, if you are looking for a task-related component, you may want to epoch beforehand, so you are only performing ICA on the data that you are interested in.
Either way, it is really important for the data to be as clean as possible, and any crazy noise to be removed before performing ICA.
Thanks Claire Miller,
What is the difference if we run ICA to one dataset and then import the weight matrix to other dataset or we have to run ICA to each dataset?
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