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Resting state fMRI (RS-fMRI; fcMRI) Physiological underpinnings Methodology Areas of investigation, some results Unresolved questions Z. Snyder July 20, 2010. Why study the resting state?
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Resting state fMRI (RS-fMRI; fcMRI) • Physiological underpinnings • Methodology • Areas of investigation, some results • Unresolved questions • Z. Snyder • July 20, 2010
Why study the resting state? Conventional task-related fMRI images the representation of cognitive processes (e.g., “attention”, “control”, “perception”) the identity of which is presumed to be known. Resting state studies target intrinsic activity, i.e., internal communication within the brain without a priori assignment of psychological labels.
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fcMRI: imaging the spatial structure of spontaneous (intrinsic) BOLD fluctuations. • Two principal techniques: • Seed-ROI-based correlation mapping • Spatial ICA
Algebraic formulae for fcMRI maps regression image: I(x)f(x)=f(t)I(x,t)/2f correlation image: rI(x)f(x)=f(t)I(x,t)/[fI(x)] Fisher z-transform: zI(x)f(x) =0.5ln[(1+ rf(x))/(1- rf(x))] = tanh-1(rI(x)f(x))
Generation of Resting State Correlation Maps Z score, fixed effects, N = 10
Ray Cooper, H. J. Crow, W. Grey Walter, A. L. Winter Brain Res. 1966:3:174-92
Ray Cooper, H. J. Crow, W. Grey Walter, A. L. Winter Brain Res. 1966:3:174-92 Fig. 8
E. V. Golanov, Y. Yamamoto, D. J. Reis Am. J. Phsyiol. 1994:266:204-14
rCBF and the BOLD signal unequivocally reflect neuronal acitvity, specifically [gamma-band] LFPs and slow cortical potentials (SCPs). That said, fMRI signals are contaminated by physiological artifacts, i.e., spurious (non-neuronal) sources of variance: pCO2 fluctuations cardiac and respiratory pulsations eye movements head motion Critical point: This spurious variance cannot be reduced simply by averaging, as in conventional fMRI.
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TC30273 fcMRI timeseries sd1 (excluding selected frames) Z = +12 scale max = 2% before fcMRI preprocessing after fcMRI preprocessing
Uses of fcMRI • investigate normal physiology - intrinsic (not task-evoked) neural activity at the systems level • topographic of organization (RSNs) • relation to conventional fMRI • relation to WM tracts • development, aging • arousal state, anesthesia, cognitive state • pathophysiology of disease • effects of experience and training
Uses of fcMRI • investigate normal physiology - intrinsic (not task-evoked) neural activity at the systems level • topographic of organization (RSNs) • relation to conventional fMRI • relation to WM tracts • development, aging • arousal state, anesthesia, cognitive state • pathophysiology of disease • effects of experience and training
Di Martino et al., CerCor 2008;18:2735-47
Uses of fcMRI • investigate normal physiology - intrinsic (not task-evoked) neural activity at the systems level • topographic of organization (RSNs) • relation to conventional fMRI • relation to WM tracts • development, aging • arousal state, anesthesia, cognitive state • pathophysiology of disease • effects of experience and training
Uses of fcMRI • investigate normal physiology - intrinsic (not task-evoked) neural activity at the systems level • topographic of organization (RSNs) • relation to conventional fMRI • relation to WM tracts • development, aging • arousal state, anesthesia, cognitive state • pathophysiology of disease • effects of experience and training