On Tue, 18 Sep 2007 15:55:15 +0100, alistair galley
<[log in to unmask]> wrote:
>apologies if this has been covered (i couldnt see it in the 100 or so
>movement parameter related messages i surveyed)
>from what i gather, including movement movement parameters in the design
>matrix is a good idea even if you have already
>realigned because it can remove additional artifacts not removed by rigid
>body transformations, assuming that your movement params
>are not correlated with your regressors of interest.
>but this only regresses out artifacts, it does not regress out the bold
>activity which may be underlying some of the movement.
>so i was thinking, wouldnt it make sense to convolve the movement
>with the hrf to model some of the underlying neuronal
>causes of the movement. obviously the same caveat would apply with regard
>these regressors not being correlated with your
>regressors of interest.
>does this make sense as something to do and has anyone done this?
People do not typically do this, as far as I know. My overall take is
that I wouldn't do this, myself.
I can't see any reason why it would be a _really bad_ idea, but it's not
clear to me that it would help much.
As you probably know, the main concern is "regressing out" the effect of
motion itself, because the changes in signal it can lead to are relatively
Finally, were you to attempt to do what you suggest, you'd have to
consider whether you'd really want to convolve the position parameters
themselves with the HRF, or something like their first order differences
(which would be velocity).
>with very best wishes