HRF Shape after GLM
This may be a simple question, but I am still very new to Homer. After I run my processing stream with the GLM, using same parameters shown in the training, my HRF shows as a series of gaussians (see attached!), different from what I've seen in the videos. Is it normal? How can I have a good visual representation of the HRF for the purpose of publication?
Thank you very much!
@bdalcinbalda, the amplitude you get is too low (1e-13), is this perhaps a short separation channel that is regressed out? Are all your channels look like this?
Thank you for your answer. Yes, I did have short channels that should have been regressed out...and all my channels look like this.
Just to explain a bit better, that low amplitude is in all channels and all subjects, but only when I do GLM instead of block averaging. If I select an actual SS detector in the probe window, I do see the flat line indicating it has been regressed out, but I still have that same amplitude range for the rest. Should I change any parameters? I currently have the default 15.0 under SSThresh if that makes a difference. My long channels are roughly 30 mm apart, and short should be 8 mm.
Also, is it normal to see that shape of HRF after modelling with gaussian basis function?
Thank you very much,