Does functional MRI detect activation in white matter? A review of emerging evidence, issues, and future directions

Gawryluk, Jodie R.; Mazerolle, Erin L.; D’Arcy, Ryan C.N.

doi:10.3389/fnins.2014.00239

Cited by 207 publications

(200 citation statements)

References 107 publications

(155 reference statements)

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“…In general, evoked signals in the white matter are lower in magnitude than cortical responses but have a similar response shape, 52,[66][67][68][69][70][71][72][73][74] consistent with our data (Fig. 7A and 7B).…”

Section: Bold Signals White Matter and Other Imaging Modalitiessupporting

confidence: 81%

Abnormal White Matter Blood-Oxygen-Level–Dependent Signals in Chronic Mild Traumatic Brain Injury

Astafiev

Shulman

Metcalf

et al. 2015

Journal of Neurotrauma

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Concussion, or mild traumatic brain injury (mTBI), can cause persistent behavioral symptoms and cognitive impairment, but it is unclear if this condition is associated with detectable structural or functional brain changes. At two sites, chronic mTBI human subjects with persistent post-concussive symptoms (three months to five years after injury) and age-and education-matched healthy human control subjects underwent extensive neuropsychological and visual tracking eye movement tests. At one site, patients and controls also performed the visual tracking tasks while blood-oxygen-leveldependent (BOLD) signals were measured with functional magnetic resonance imaging. Although neither neuropsychological nor visual tracking measures distinguished patients from controls at the level of individual subjects, abnormal BOLD signals were reliably detected in patients. The most consistent changes were localized in white matter regions: anterior internal capsule and superior longitudinal fasciculus. In contrast, BOLD signals were normal in cortical regions, such as the frontal eye field and intraparietal sulcus, that mediate oculomotor and attention functions necessary for visual tracking. The abnormal BOLD signals accurately differentiated chronic mTBI patients from healthy controls at the single-subject level, although they did not correlate with symptoms or neuropsychological performance. We conclude that subjects with persistent post-concussive symptoms can be identified years after their TBI using fMRI and an eye movement task despite showing normal structural MRI and DTI.

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Section: Bold Signals White Matter and Other Imaging Modalitiessupporting

confidence: 81%

Abnormal White Matter Blood-Oxygen-Level–Dependent Signals in Chronic Mild Traumatic Brain Injury

Astafiev

Shulman

Metcalf

et al. 2015

Journal of Neurotrauma

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“…It is also shown that there might be relation between VLF differences on white matter and BOLD signal detection (Gawryluk, Mazerolle, & D'Arcy, 2014). The epilepsy patients’ functional connectivity of resting state BOLD signal also reduced within DMN, and between epileptic areas and DMN (Constable et al., 2013; J. Gotman et al., 2005; Lee, Smyser, et al., 2013; Robinson et al., 2017).…”

Section: Discussionmentioning

confidence: 99%

Altered physiological brain variation in drug‐resistant epilepsy

et al. 2018

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IntroductionFunctional magnetic resonance imaging (fMRI) combined with simultaneous electroencephalography (EEG‐fMRI) has become a major tool in mapping epilepsy sources. In the absence of detectable epileptiform activity, the resting state fMRI may still detect changes in the blood oxygen level‐dependent signal, suggesting intrinsic alterations in the underlying brain physiology.MethodsIn this study, we used coefficient of variation (CV) of critically sampled 10 Hz ultra‐fast fMRI (magnetoencephalography, MREG) signal to compare physiological variance between healthy controls (n = 10) and patients (n = 10) with drug‐resistant epilepsy (DRE).ResultsWe showed highly significant voxel‐level (p < 0.01, TFCE‐corrected) increase in the physiological variance in DRE patients. At individual level, the elevations range over three standard deviations (σ) above the control mean (μ) CVMREG values solely in DRE patients, enabling patient‐specific mapping of elevated physiological variance. The most apparent differences in group‐level analysis are found on white matter, brainstem, and cerebellum. Respiratory (0.12–0.4 Hz) and very‐low‐frequency (VLF = 0.009–0.1 Hz) signal variances were most affected.ConclusionsThe CVMREG increase was not explained by head motion or physiological cardiorespiratory activity, that is, it seems to be linked to intrinsic physiological pulsations. We suggest that intrinsic brain pulsations play a role in DRE and that critically sampled fMRI may provide a powerful tool for their identification.

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“…42 WM fMRI is known to suffer from very low signal to noise due to the much smaller vascular volume in WM compared to GM. Our finding that CA-related changes are twice as large for WM perpendicular to B 0 compared to WM parallel to B 0 can be translated directly to the BOLD of the MRI signal.…”

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confidence: 99%

Anisotropic cerebral vascular architecture causes orientation dependency in cerebral blood flow and volume measured with dynamic susceptibility contrast magnetic resonance imaging

Hernández‐Torres

Kassner

Forkert

et al. 2016

J Cereb Blood Flow Metab

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Measurements of cerebral perfusion using dynamic susceptibility contrast magnetic resonance imaging rely on the assumption of isotropic vascular architecture. However, a considerable fraction of vessels runs in parallel with white matter tracts. Here, we investigate the effects of tissue orientation on dynamic susceptibility contrast magnetic resonance imaging. Tissue orientation was measured using diffusion tensor imaging and dynamic susceptibility contrast was performed with gradient echo planar imaging. Perfusion parameters and the raw dynamic susceptibility contrast signals were correlated with tissue orientation. Additionally, numerical simulations were performed for a range of vascular volumes of both the isotropic vascular bed and anisotropic vessel components, as well as for a range of contrast agent concentrations. The effect of the contrast agent was much larger in white matter tissue perpendicular to the main magnetic field compared to white matter parallel to the main magnetic field. In addition, cerebral blood flow and cerebral blood volume were affected in the same way with angle-dependent variations of up to 130%. Mean transit time and time to maximum of the residual curve exhibited weak orientation dependency of 10%. Numerical simulations agreed with the measured data, showing that one-third of the white matter vascular volume is comprised of vessels running in parallel with the fibre tracts.

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Does functional MRI detect activation in white matter? A review of emerging evidence, issues, and future directions

Cited by 207 publications

References 107 publications

Abnormal White Matter Blood-Oxygen-Level–Dependent Signals in Chronic Mild Traumatic Brain Injury

Abnormal White Matter Blood-Oxygen-Level–Dependent Signals in Chronic Mild Traumatic Brain Injury

Altered physiological brain variation in drug‐resistant epilepsy

Anisotropic cerebral vascular architecture causes orientation dependency in cerebral blood flow and volume measured with dynamic susceptibility contrast magnetic resonance imaging

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