[Eeglablist] Question on filter order in the basic FIR filter and low pass cut-off

[Coetzee, AM, Mr [andrecoetzee@sun.ac.za]]

Good day all

I hope you are doing well. I am a master's student from South Africa busy doing my thesis using continuous EEG and gait analysis during separate forward and backward 6-minute walk test trials over a 10 meter walking distance in people with Parkinson's disease (PD). For my data I am not interested in the data from turns, so this data has been removed, leaving me with a data set duration across all four trials combined (2x forward & 2x backward) of roughly 1350 seconds per dataset before preprocessing.

I am in the process of analysing my data and I have a question about some of the options in the basic FIR filter on EEGLAB. Amongst other frequencies such as theta, alpha and beta, I am also interested in studying the PSD of gamma, so what would be the best low pass cut-off to utilise in this instance if I am also interested in gamma, taking into account that I am doing a gait task? There aren't too many studies I have seen that have done an EEG gait task in people with PD, and of the few I have seen some authors utilise low-pass cut-offs anywhere from 40 Hz up to as high as 200 Hz.

A second question I have is regarding the filter order option within the basic FIR filter tool, this part I do not understand too well and do not know what I should input here, so I was hoping someone might be able to explain it better to me. How do I go about determining what the filter order should be for my data, if for instance one uses cut-offs such as those mentioned above (e.g.: 1 - 40 Hz or 1 - 200 Hz)? Or should I just be using the default automatic?

I would greatly appreciate any advice I can receive. Thank you for your time.

Kind regards

André Coetzee | MSc. student in Sport Science | Division of Movement Science and Exercise Therapy, Department of Exercise, Sport and Lifestyle Medicine | Registered Biokineticist (BK0031020)

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