Linear Mixed-Effects Modeling Approach to FMRI Group Analysis.

Scientific and Statistical Computing Core, NIMH/NIH/HHS, USA. Electronic address: .
NeuroImage (Impact Factor: 6.36). 01/2013; 73. DOI: 10.1016/j.neuroimage.2013.01.047
Source: PubMed


Conventional group analysis is usually performed with Student-type t-test, regression, or standard AN(C)OVA in which the variance-covariance matrix is presumed to have a simple structure. Some correction approaches are adopted when assumptions about the covariance structure is violated. However, as experiments are designed with different degrees of sophistication, these traditional methods can become cumbersome, or even be unable to handle the situation at hand. For example, most current FMRI software packages have difficulty analyzing the following scenarios at group level: (1) taking within-subject variability into account when there are effect estimates from multiple runs or sessions; (2) continuous explanatory variables (covariates) modeling in the presence of a within-subject (repeated measures) factor, multiple subject-grouping (between-subjects) factors, or the mixture of both; (3) subject-specific adjustments in covariate modeling; (4) group analysis with estimation of hemodynamic response (HDR) function by multiple basis functions; (5) various cases of missing data in longitudinal studies; and (6) group studies involving family members or twins.

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    • "Further development of FATCAT will include approaches for utilizing along-tract statistics in characterizing individuals' white matter properties. Also, in order to be able to account for missing data in group tables, future versions will utilize linear mixed effects (LME) modeling using AFNI's 3dLME [Chen et al. 2013]. It is also expected that, as has already happened since the initial FATCAT release, further analysis tools will be developed in response to users' requests. "
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    DESCRIPTION: Updates and examples of combining FATCAT, SUMA and AFNI, including: a new "mini-probabilistic" approach to tractography (as an improvement to the standard deterministic methodology); descriptions of new user-interactive visualization tools, particularly for functional and structural network connectivity, combining AFNI and SUMA; and approaches for performing group analysis of FMRI/DTI networks using 3dMVM and FATCAT command line tools.
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    • "fMRI activity evoked by each task type was explored by constraining linear mixed-effects model analyses (3dLME; Chen et al., 2013) within the localizer-identified ROIs (separate analyses performed for each localizer ROI). Statistical maps for task type were created using the contrast of texture-location versus texture-type, with positive BOLD activations corresponding to regions more active in response to texture-location and negative BOLD activations corresponding to regions more active in response to texture-type. "
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    ABSTRACT: Everyday objects are often composed of multiple parts, each with a unique surface texture. The neural substrates mediating the integration of surface features on different object parts are not fully understood, and potential contributions by both the ventral and dorsal visual pathways are possible. To explore these substrates, we collected fMRI data while human participants performed a difference detection task on two objects with textured parts. The objects could either differ in the assignment of the same texture to different object parts ("texture-location") or the types of texture ("texture-type"). In the ventral stream, comparable BOLD activation levels were observed in response to texture-location and texture-type differences. In contrast, in a priori localized spatial processing regions of the dorsal stream, activation was greater for texture-location than texture-type differences, and the magnitude of the activation correlated with behavioral performance. We confirmed the reliance of surface texture to object part mapping on spatial processing mechanisms in subsequent psychophysical experiments, in which participants detected a difference in the spatial distance of an object relative to a reference line. In this task, distracter objects occasionally appeared, which differed in either texture-location or texture-type. Distracter texture-location differences slowed detection of spatial distance differences, but texture-type differences did not. More importantly, the distracter effects were only observed when texture-location differences were presented within whole shapes and not between separated shape parts at distinct spatial locations. We conclude that both the mapping of texture features to object parts and the representation of object spatial position are mediated by common neural substrates within the dorsal visual pathway.
    Journal of Cognitive Neuroscience 09/2015; DOI:10.1162/jocn_a_00871 · 4.09 Impact Factor
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    • "Brain imaging analysis focused on the anticipatory phase of the task. Linear mixed-effects (LME) analyses were conducted using AFNI's 3dLME (Chen et al., 2013) for the anticipatory phase of the task. Medication (placebo, varenicline) and imagetype (alcohol, food, neutral) were fixed effects in the model and individual participants were treated as random effects. "
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    ABSTRACT: Preclinical and emerging clinical evidence indicates that varenicline, a nicotinic partial agonist approved for smoking cessation, attenuates alcohol seeking and consumption. Reductions of alcohol craving have been observed under varenicline treatment and suggest effects of the medication on alcohol reward processing, but this hypothesis remains untested. In this double-blind, placebo-controlled randomized experimental medicine study, 29 heavy drinkers underwent a functional magnetic resonance imaging scan after 2 weeks of varenicline (2mg/d) or placebo administration. During functional magnetic resonance imaging, participants performed the Alcohol-Food Incentive Delay task, where they could earn points for snacks or alcohol. At baseline and after 3 weeks of medication, participants underwent intravenous alcohol self-administration sessions in the laboratory. During the functional magnetic resonance imaging scan, participants in the varenicline group (N=17) reported lower feelings of happiness and excitement on subjective mood scales when anticipating alcohol reward compared with the placebo group (N=12). Linear mixed effects analysis revealed that anticipation of alcohol reward was associated with significant blood oxygen level dependent activation of the ventral striatum, amygdala, and posterior insula in the placebo group; this activation was attenuated in the varenicline group. The varenicline group showed no difference in intravenous alcohol self-administration relative to the placebo group for either session. Participants with higher insula activation when anticipating alcohol reward showed higher alcohol self-administration behavior across groups. Our findings suggest that varenicline decreases blood oxygen level dependent activation in striato-cortico-limbic regions associated with motivation and incentive salience of alcohol in heavy drinkers. This mechanism may underlie the clinical effectiveness of varenicline in reducing alcohol intake and indicates its potential utility as a pharmacotherapy for alcohol use disorders. Published by Oxford University Press on behalf of CINP 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.
    The International Journal of Neuropsychopharmacology 07/2015; DOI:10.1093/ijnp/pyv068 · 4.01 Impact Factor
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