Effect of spatial smoothing on physiological noise in high-resolution fMRI

Triantafyllou, Christina; Hoge, Richard D.; Wald, Lawrence L.

doi:10.1016/j.neuroimage.2006.04.182

Cited by 126 publications

(129 citation statements)

References 8 publications

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“…Resting state functional data were acquired using a T2*-weighted EPI pulse sequence (TR = 6 sec, TE = 30 msec, α = 90°, FOV = 256 mm, matrix = 128 × 128, slice thickness = 2 mm, 67 near-axial slices). Resting data were acquired at higher resolution (2 mm isotropic) to reduce the relative influence of physiological noise (Triantafyllou, Hoge, & Wald, 2006;Triantafyllou et al, 2005). This necessitated a somewhat high TR, which is justified by the observation that most of the power in resting state fluctuations is in frequencies lower than our sampling rate.…”

Section: Data Acquisitionmentioning

confidence: 99%

Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

Deen

Saxe

Bedny

2015

Journal of Cognitive Neuroscience

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Abstract■ In congenital blindness, the occipital cortex responds to a range of nonvisual inputs, including tactile, auditory, and linguistic stimuli. Are these changes in functional responses to stimuli accompanied by altered interactions with nonvisual functional networks? To answer this question, we introduce a data-driven method that searches across cortex for functional connectivity differences across groups. Replicating prior work, we find increased fronto-occipital functional connectivity in congenitally blind relative to blindfolded sighted participants. We demonstrate that this heightened connectivity extends over most of occipital cortex but is specific to a subset of regions in the inferior, dorsal, and medial frontal lobe. To assess the functional profile of these frontal areas, we used an n-back working memory task and a sentence comprehension task. We find that, among prefrontal areas with overconnectivity to occipital cortex, one left inferior frontal region responds to language over music. By contrast, the majority of these regions responded to working memory load but not language. These results suggest that in blindness occipital cortex interacts more with working memory systems and raise new questions about the function and mechanism of occipital plasticity. ■

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Section: Data Acquisitionmentioning

confidence: 99%

Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

Deen

Saxe

Bedny

2015

Journal of Cognitive Neuroscience

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“…Finally, to assess the influence of these noise reduction strategies on the signal at a more basic level, we measured the tSNR (Triantafyllou et al, 2006;Van Dijk et al, 2012).…”

Section: Metricsmentioning

confidence: 99%

Using Edge Voxel Information to Improve Motion Regression for rs-fMRI Connectivity Studies

2015

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Recent fMRI studies have outlined the critical impact of in-scanner head motion, particularly on estimates of functional connectivity. Common strategies to reduce the influence of motion include realignment as well as the inclusion of nuisance regressors, such as the 6 realignment parameters, their first derivatives, time-shifted versions of the realignment parameters, and the squared parameters. However, these regressors have limited success at noise reduction. We hypothesized that using nuisance regressors consisting of the principal components (PCs) of edge voxel time series would be better able to capture slice-specific and nonlinear signal changes, thus explaining more variance, improving data quality (i.e., lower DVARS and temporal SNR), and reducing the effect of motion on default-mode network connectivity. Functional MRI data from 22 healthy adult subjects were preprocessed using typical motion regression approaches as well as nuisance regression derived from edge voxel time courses. Results were evaluated in the presence and absence of both global signal regression and motion censoring. Nuisance regressors derived from signal intensity time courses at the edge of the brain significantly improved motion correction compared to using only the realignment parameters and their derivatives. Of the models tested, only the edge voxel regression models were able to eliminate significant differences in default-mode network connectivity between high-and low-motion subjects regardless of the use of global signal regression or censoring.

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“…A method to mitigate physiological noise is to average the signal change over time over numerous pixels, because the physiological noise over an area is only somewhat correlated (37). Because H 2 17 O is produced over the entire brain, the H 2 17 O sig- Fig.…”

Section: Comparison Ofmentioning

confidence: 99%

Mapping of cerebral oxidative metabolism with MRI

Mellon

Beesam

Elliott

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Using a T 1ρ MRI based indirect detection method, we demonstrate the detection of cerebral oxidative metabolism and its modulation by administration of the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) in a large animal model with minimum utilization of 17 O 2 gas. The study was performed by 17 O 2 inhalation in swine during imaging on clinical MRI scanners. Metabolic changes in swine were determined by two methods. First, in a series of animals, increased metabolism caused by DNP injection was measured by exhaled gas analysis. The average whole-body metabolic increase in seven swine was 11.9% þ ∕ − 2.5% per mg∕kg, stable over three hours. Secondly, hemispheric brain measurements of oxygen consumption stimulated by DNP injection were made in five swine using T 1ρ MRI following administration of 17 O 2 gas. Metabolism was calculated from the change in the T 1ρ weighted MRI signal due to H 2 17 O generated from 17 O 2 inhalation before and after doubling of metabolism by DNP. These results were confirmed by direct oxygen-17 MR spectroscopy, a gold standard for in vivo H 2 17 O measurement. Overall, this work underscores the ability of indirect oxygen-17 imaging to detect oxygen metabolism in an animal model with a lung capacity comparable to the human with minimal utilization of expensive 17 O 2 gas. Given the demonstrated high efficiency in use of 17 O 2 and the proven feasibility of performing such measurements on standard clinical MRI scanners, this work enables the adaption of this technique for human studies dealing with a broad array of metabolic derangements.2,4-dinitrophenol | cerebral metabolic rate of oxygen consumption | CMRO2 | oxygen-17 D erangement of oxidative metabolism is noted in numerous conditions including Alzheimer's disease, cerebral ischemia, cancer, and aging. Despite the known derangements in oxidative metabolism that occur in many diseases, there are still no routine clinical, nonradioactive technologies that directly assess oxidative metabolism. To address this need, a number of studies have investigated techniques based on 17 O, the only stable, naturally occurring, NMR-visible isotope of oxygen. These techniques utilize either proton detection of 17 O through the strong 1 H-17 O J-coupling in water (1), termed "indirect" imaging (2-5), or "direct" spectroscopy based upon imaging of the 17 O nucleus in H 2 17 O (6-10).While the direct detection methods are highly specific to 17 O, their inherent low SNR requires either long acquisition times or ultrahigh magnetic fields, which precludes their implementation in the routine clinical setting. In contrast, indirect detection methods exploit the higher sensitivity of proton MR and can be implemented on routine clinical scanners. Using both direct and indirect 17 O MR detection methods, oxidative metabolism has been demonstrated in small animals such as cats, rats, and mice (4, 11-13). To date there have been only two published abstracts of direct 17 O NMR studies of healthy humans (14, 15). There have been no reports of indirect de...

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Effect of spatial smoothing on physiological noise in high-resolution fMRI

Cited by 126 publications

References 8 publications

Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

Using Edge Voxel Information to Improve Motion Regression for rs-fMRI Connectivity Studies

Mapping of cerebral oxidative metabolism with MRI

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