[VoxBo] covariates of no interest

[meeri at sas.upenn.edu]

Hello, I have a question about designing the G matrix and adding a single
covariate of no interest.  Does it matter what scale we use for our covariate?
For instance, working with time series, we are trying to remove heartbeat as a
covariate of no interest from our rCBF signal.  However, rCBF is in dB, while
heartbeat is in beats per minute... Should we rescale in terms of percentage
change of heartbeat, or something else perhaps?

Thanks,
Meeri