[Eeglablist] Decimation prior to ICA and related things

[Modestino, Edward J *HS]

Dear EEGLAB experts,

(1) Is it true that  ICA must be subject, like all the model-based spectral analysis methods, to a recommendation that one decimate to the lowest frequency capable of representing the actual signal content of the data without alienation effects?  Does one NEED to decimate the data before running ICA?  For instance, we have a data set recorded at 1,000 Hz.  Do we need to decimate this to approximately 128 or 256?

(2 ) According to the formula that Dr. Makeig gave to determine the optimal amount of data,  #timepoints/(#channels)^2, it would appear that a higher sampling rate will give better ICA results.  Is this the case?

(3) Finally, using this formula, #timepoints/(#channels)^2, is there a threshold or cutoff one needs to be exceeded to have the optimal amount of data to run ICA. Simply doing the equation without any way to interpret the output is not helpful.

Thanks for your help,
Dr. Modestino

Edward Justin Modestino, Ph.D.
Postdoctoral Research Associate
Ray Westphal Neuroimaging Laboratory
Division of Perceptual Studies
Department of Psychiatry and Neurobehavioral Sciences
University of Virginia
Email: ejm9f at virginia.edu


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