Simulation of the Effects of Global Normalization Procedures in Functional MRI

Gavrilescu, Maria; Shaw, Marnie; Stuart, G. W.; Eckersley, Peter; Svalbe, Imants; Egan, Gary F.

doi:10.1006/nimg.2002.1226

Cited by 74 publications

(62 citation statements)

References 10 publications

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“…To account for potential indeterminate noise, 23,24 we also identified seeds of CSF and white matter on each individual functional EPI, and their time courses were added as covariates of no interest (nuisance) into each of the seed-ROI voxelwise correlation analyses to remove nonneural contributions to the blood oxygen level-dependent signal and thus enhance specificity. Similarly, the age of the study participants and volumes of the specific seeds were entered as nuisance covariates.…”

Section: Image Processing and Data Analysismentioning

confidence: 99%

Disrupted Resting-State Functional Connectivity in Progressive Supranuclear Palsy

Piattella

Tona

Bologna

et al. 2015

AJNR Am J Neuroradiol

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Section: Image Processing and Data Analysismentioning

confidence: 99%

Disrupted Resting-State Functional Connectivity in Progressive Supranuclear Palsy

Piattella

Tona

Bologna

et al. 2015

AJNR Am J Neuroradiol

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“…A general linear model (Friston, et al 1995), and a box-car design convolved with a canonical hemodynamic response function (HRF) were used to calculate the activation maps. Since global normalization in SPM can produce false deactivation signals (Aguirre, et al 1998;Gavrilescu, et al 2002), the BOLD signal strength was estimated without the removal of global effects. The time series were band-pass filtered with the HRF as low pass filter, and an additional high-pass filter (cut-off frequency: 1/126Hz for WM, 1/256 for VA).…”

Section: Data Processingmentioning

confidence: 99%

Common deactivation patterns during working memory and visual attention tasks: An intra‐subject fMRI study at 4 Tesla

Tomasi¹,

Ernst²,

Caparelli³

et al. 2006

Human Brain Mapping

197

143

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This parametric functional magnetic resonance imaging (fMRI) study investigates the balance of negative, and positive fMRI signals in the brain. A set of visual attention (VA) and of working memory (WM) tasks with graded levels of difficulty was used to deactivate separate, but overlapping networks that include the frontal, temporal, occipital, and limbic lobes; regions commonly associated with auditory and emotional processing. Brain activation (% signal change, and volume) was larger for VA tasks than for WM tasks, but deactivation was larger for WM tasks. BOLD responses crosscorrelated strongly in the deactivated network during VA but less so during WM. The variability of the deactivated network across different cognitive tasks supports the hypothesis that global CBF vary across different tasks, but not between conditions of the same task. The task-dependent balance of activation and deactivation might allow maximization of resources for the activated network.

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“…No global scaling (Della-Maggiore, Chau, Peres-Neto, & McIntosh, 2002;Gavrilescu et al, 2002) and no low-pass filtering were used.…”

Section: Fmri Acquisition and Analysismentioning

confidence: 99%

Toward a taxonomy of attention shifting: Individual differences in fMRI during multiple shift types

Wager

Jonides

Smith

et al. 2005

Cognitive, Affective, & Behavioral Neuroscience

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Although task switching is often considered one of the fundamental abilities underlying executive functioning and general intelligence, there is little evidence that switching is a unitary construct and little evidence regarding the relationship between brain activity and switching performance. We examined individual differences in multiple types of attention shifting in order to determine whether behavioral performance and fMRI activity are correlated across different types of shifting. The participants (nϭ 39) switched between objects and attributes both when stimuli were perceptually available (external) and when stimuli were stored in memory (internal). We found that there were more switchrelated activations in many regions associated with executive control-including the dorsolateral and medial prefrontal and parietal cortices-when behavioral switch costs were higher (poor performance). Conversely, activation in the ventromedial prefrontal cortex (VMPFC) and the rostral anterior cingulate was consistently correlated with good performance, suggesting a general role for these areas in efficient attention shifting. We discuss these findings in terms of a model of cognitive-emotional interaction in attention shifting, in which reward-related signals in the VMPFC guide efficient selection of tasks in the lateral prefrontal and parietal cortices. WAGER, JONIDES, SMITH, AND NICHOLStasks can be dissociated on the basis of three factors: (1) Among what representations is attention shifted? (2) In what locus are the items between which attention is shifted stored-in WM or in perceptual buffers? (3) And finally, when does the shift occur-when an actual stimulus is presented and a behavioral response is required, or in advance of stimulus presentation and response selection? What Representations and What Locus of Storage?Theories of switching have combined evidence on switch costs from studies varying the cue type (Coull, Frith, Buchel, & Nobre, 2000), the target tasks (Allport, Styles, & Hsieh, 1994;Rubinstein, Meyer, & Evans, 2001), and whether switching occurs among the tasks themselves (i.e., both stimulus and response sets), operations (Spector & Biederman, 1976), stimulus-response mapping rules (Rubinstein et al., 2001), objects stored in WM (Garavan, 1998), object attributes (Owen, Roberts, Polkey, Sahakian, & Robbins, 1991;Rogers & Monsell, 1995), or combinations of these. The question of consistency across types is critical if particular shifting tasks are used as measures of an executive ability.In this study, we combined two types of evidence that have been considered for understanding the relationships between types of shifting: individual differences in performance and brain-imaging activation. In individualdifferences studies, the basic measures of performance are the reaction time (RT) and error rate costs for trials in which a shift of attention is required, as compared with trials with no shift (i.e., shift-no shift; see, e.g., Garavan, 1998;Gopher, Armony, & Greenshpan, 2000;Meiran, Chorev, & Sapir, 2...

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Simulation of the Effects of Global Normalization Procedures in Functional MRI

Cited by 74 publications

References 10 publications

Disrupted Resting-State Functional Connectivity in Progressive Supranuclear Palsy

Disrupted Resting-State Functional Connectivity in Progressive Supranuclear Palsy

Common deactivation patterns during working memory and visual attention tasks: An intra‐subject fMRI study at 4 Tesla

Toward a taxonomy of attention shifting: Individual differences in fMRI during multiple shift types

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