Dear SPM-community,
We are using DCM for induced responses to study movement underlying neuronal oscillations. Using SPM12, we are currently facing what seems to be an edge artefact in the time-frequency plots (see attached, sampling rate: 500Hz, Wavelet, cycle n.: 7; preprocessing: epoching (-600 1000ms), high-pass filter: 1Hz, downsampling: 5000Hz to 500Hz, low-pass filter: 48 Hz, baseline-correction: -600 to 0; stopband-filter: 49-51 Hz; individual MRI-coregistering;).
We have tried to change the wavelet cycle number and to increase the downsampling (DCM-function "subsample": 2, 3, 4, 5). With data downsampled to 134 Hz (subsample 4) partly seemd to ameliorate the results, whereas subsample 2, 3 or 5 didnĀ“t change results.
- Despite this and the filtering, may we be facing an aliasing artefact or ringing artefact?
- May this arise through SPM-DCM source reconstruction?
- May some of our preprocessing-procedure cause these artefacts?
Any suggestions or sharing similiar problems is much appreciated.
Carlo
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