If you've not already found them, these articles may be helpful to you in understanding the issues around global signal regression:
Fox MD, Zhang D, Snyder AZ, & Raichle ME (2009). The global signal and observed anticorrelated resting state brain networks., Journal of neurophysiology 101, 3270–3283.
Murphy K, Birn RM, Handwerker DA, Jones TB, & Bandettini PA (2009). The impact of global signal regression on resting state correlations: are anti-correlated networks introduced?, NeuroImage 44, 893–905.
Weissenbacher A, Kasess C, Gerstl F, Lanzenberger R, Moser E, & Windischberger C (2009). Correlations and anticorrelations in resting-state functional connectivity MRI: a quantitative comparison of preprocessing strategies., NeuroImage 47, 1408–1416.
Anderson JS, Druzgal TJ, Lopez-Larson M, Jeong E-K, Desai K, & Yurgelun-Todd D (2010). Network anticorrelations, global regression, and phase-shifted soft tissue correction, Human brain mapping 32, 919–934.
Saad ZS, Gotts SJ, Murphy K, Chen G, Jo HJ, Martin A, & Cox RW (2012). Trouble at rest: how correlation patterns and group differences become distorted after global signal regression., Brain Connectivity 2, 25–32.
The following recent article may be of interest if you are finalizing a RSFC pipeline:
Hallquist MN, Hwang K, Luna B. (2013). The nuisance of nuisance regression: spectral misspecification in a common approach to resting-state fMRI preprocessing reintroduces noise and obscures functional connectivity. NeuroImage, 82, 208–25. PMCID: PMC3759585
On Jan 24, 2014, at 2:40 AM, Mauricio Delgado <[log in to unmask]> wrote:
> Dear FSL group,
> As you may know there is considerable debate regarding global signal regression in resting-state fMRI analysis. Though several methods have been proposed for removing physiological noise out of the data instead of global signal regression, there is no standard method for doing so. Hence, I am wondering what the preferred strategy of the FSL group would be when conducting a seed-based resting-state fMRI analysis?
> Additionally, is it correct that global signal regression would only increase the probability of artifactual anticorrelations (negative functional connectivity), while having no adverse effects on, or even improve, positive correlations?
> Thanks for your time and effort!
> Mauricio Delgado
Colm G. Connolly, Ph. D.
Dept of Psychiatry
University of California, San Francisco
401 Parnassus Avenue,
San Francisco, CA 94143