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

Yarkoni, Tal; Barch, Deanna M.; Gray, Jeremy R.; Conturo, Thomas E.; Braver, Todd S. · 2009 · OpenAlex-citations

DOI: 10.1371/journal.pone.0004257

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study addresses the underutilization of trial-by-trial reaction time (RT) variability as a predictor in functional magnetic resonance imaging (fMRI) analyses. While RT is a standard performance metric in psychology, few neuroimaging studies have examined its relationship with brain activation across diverse tasks. The authors sought to identify task-general neural correlates of RT variability, testing three theoretical predictions: that longer RTs might reflect delayed onset of physiological processes, increased duration of processing (leading to greater BOLD amplitude via linear summation), or decreased amplitude due to reduced cognitive effort. To test these hypotheses, the researchers reanalyzed data from five distinct fMRI experiments involving 252 healthy young adults. The datasets spanned various cognitive tasks, including working memory, decision-making, emotion rating, and memory encoding, using different stimulus modalities and scanner strengths (1.5T and 3T). Using a general linear model approach, the authors modeled standardized RT values as parametric regressors. To avoid assumptions about the hemodynamic response shape, they employed a Finite Impulse Response (FIR) basis set to estimate RT effects at seven discrete time points post-stimulus. They identified regions showing consistent RT-related activation across all five studies using a conjunction analysis and further characterized these effects using linear contrasts for temporal shifts and amplitude changes. The results revealed consistent RT-related activation in widespread gray and white matter regions. In gray matter, particularly in frontal, parietal, and visual areas, activation showed a temporal shift, indicating delayed initiation of processing on trials with longer RTs. Additionally, frontal regions exhibited a positive correlation between RT and activation amplitude, consistent with a "time-on-task" effect where sustained processing leads to greater BOLD summation. Surprisingly, the study also identified reliable RT-related signals in white matter regions, including the corpus callosum and corona radiata. These white matter signals were characterized by smaller amplitudes and significantly delayed time-to-peak compared to gray matter, primarily reflecting delayed onset rather than amplitude changes. The findings demonstrate that modeling trial-by-trial RT variability is crucial for accurate fMRI analysis, as it captures systematic neural dynamics often overlooked. The study provides robust evidence that RT variability modulates BOLD signals in both gray and white matter. Specifically, it suggests that RT variability can serve as a powerful probe for detecting the elusive white matter BOLD signal, challenging the assumption that white matter lacks detectable metabolic activity. This multi-study approach highlights the generalizability of RT-brain activation relationships across different cognitive domains and experimental designs.

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• cognitive capacity variation