BOLD Correlates of Trial-by-Trial Reaction Time Variability in Gray and White Matter: A Multi-Study fMRI Analysis

Department of Psychology, Washington University, Saint Louis, Missouri, United States of America.
PLoS ONE (Impact Factor: 3.23). 02/2009; 4(1):e4257. DOI: 10.1371/journal.pone.0004257
Source: PubMed


Reaction time (RT) is one of the most widely used measures of performance in experimental psychology, yet relatively few fMRI studies have included trial-by-trial differences in RT as a predictor variable in their analyses. Using a multi-study approach, we investigated whether there are brain regions that show a general relationship between trial-by-trial RT variability and activation across a range of cognitive tasks.
The relation between trial-by-trial differences in RT and brain activation was modeled in five different fMRI datasets spanning a range of experimental tasks and stimulus modalities. Three main findings were identified. First, in a widely distributed set of gray and white matter regions, activation was delayed on trials with long RTs relative to short RTs, suggesting delayed initiation of underlying physiological processes. Second, in lateral and medial frontal regions, activation showed a "time-on-task" effect, increasing linearly as a function of RT. Finally, RT variability reliably modulated the BOLD signal not only in gray matter but also in diffuse regions of white matter.
The results highlight the importance of modeling trial-by-trial RT in fMRI analyses and raise the possibility that RT variability may provide a powerful probe for investigating the previously elusive white matter BOLD signal.

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    • "In order to assess trial-to-trial RT variability, we used a similar approach to Weissman et al. (2006) and Esterman et al. (2013, 2014): For each participant, the mean RT for all valid go-trials was calculated for each of the 6 blocks; trial-to-trial deviation from the mean was calculated by subtracting the RT of each go-trial from the mean RT of that block (absolute [RT-meanRT]), which is hereafter referred to as RT deviation. The rationale for using mean subtracted RT values is that RTs with greater deviation from the mean RT arguably represent atypical attention to the task: trials with RTs that deviate further from the mean are indicative of inefficient control of attention (Weissman et al., 2006; Yarkoni et al., 2009 "
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    Neuropsychologia 03/2015; 72. DOI:10.1016/j.neuropsychologia.2015.03.015 · 3.30 Impact Factor
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    • "Regionally specific effects were compared using the linear contrasts CI vs. SI and SI vs. control. A previous study demonstrated that the BOLD signals in specific regions are modulated by RT (Yarkoni et al., 2009). To rule out this possibility in the present study, the CI vs. SI contrast was also examined in a model that included the RTs as covariates. "
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    Neuropsychologia 10/2014; 66. DOI:10.1016/j.neuropsychologia.2014.10.015 · 3.30 Impact Factor
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    • "Hemodynamic response function (HRF) regressors modulated by trial-level RTs have the potential to better account for BOLD percent signal changes than the more typical nonmodulated models, thus increasing statistical power (Grinband et al., 2008). RT-modulation analyses have been used to explore a broad range of cognitive processes including selective attention (Weissman et al., 2006), spatial attention (Prado and Weissman, 2011), inhibition (Bellgrove et al., 2004), as well as shared processes across a range of cognitive tasks (Yarkoni et al., 2009). For each participant, voxel-wise analyses were carried out to obtain (1) performance-independent DSVT-related BOLD percent signal change and (2) performance-dependent triallevel RT-BOLD correlations using amplitude modulated linear deconvolution analyses (Cox, 1996). "
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