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<DIV>Hi all,<BR><BR></DIV>I have a rookie question about using ICA to remove specific artifacts. Please correct me if I was wrong.<BR><BR></DIV> (1) I should feed ICA with 'cleaned' epochs (less non-stereotypic noise) and with enough data points (> k*N^2). <BR> <BR> (2), I can calculate ICA on short epochs, then apply the ICA (weights and sphere matrices) to long epochs from the same dateset.<BR><BR></DIV>(reference link: <A href="http://sccn.ucsd.edu/wiki/Chapter_09:_Decomposing_Data_Using_ICA#Studying_and_removing_ICA_components" target=_blank data-saferedirecturl="https://www.google.com/url?hl=en&q=http://sccn.ucsd.edu/wiki/Chapter_09:_Decomposing_Data_Using_ICA%23Studying_and_removing_ICA_components&source=gmail&ust=1465415301340000&usg=AFQjCNGCpOIxZuluS29kWDRWHUIywWHIwA">http://sccn.ucsd.edu/wiki/<WBR>Chapter_09:_Decomposing_Data_<WBR>Using_ICA#Studying_and_<WBR>removing_ICA_components</A>)<BR><BR></DIV>For my data set, I want to remove the known artifacts that occurs right after the events (within 100 ms). Also, there are only 13 channels (including 2 eye-channels) for each subject.<BR></DIV>
<DIV>My goal is to remove this special artifacts using ICA on long epochs. However, because I already know the artifacts occurs shortly after events, I want ICA focus on this short window to identify the artifact-components. I want to minimize the effects of other artifacts or noise on ICA. <BR></DIV>
<DIV><BR></DIV>My current thoughts are: 1, cut continuous file into long epochs (4 seconds). <BR></DIV> <WBR> 2, remove epochs with non-stereotypic noise.<BR></DIV> <WBR> 3, 1-hz high-pass filter the remaining long epochs, then cut short epochs (-30 to 100 ms). In this way, the short epochs mainly contains the artifacts I want to remove. <BR></DIV> <WBR> 4, apply ICA on the 0.13-second short epochs. The sampling rate of our data is 1000 Hz. There are more than 50 trials. Therefore, The data point for ICA are around 1000*0.13*50 = 6500. This is larger than 5070 (30*13^2), so I should have enough data for ICA on those short epochs.<BR></DIV> <WBR> 5, identify the artifact-components from step 4.<BR></DIV> <WBR> 6, apply the ICA weights and sphere to long epochs (before 1-hz highpass filter), then reject artifact-components identified from step 5. <BR></DIV> <WBR> 7, for now, I should have long epochs that are artifact-corrected and not filtered. <BR><BR></DIV>Please let me know if those steps are reasonable. Any suggestions or comments are appreciated!<BR><BR></DIV>Thanks.
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