Introducing Alternative-Based Thresholding for Defining Functional Regions of Interest in fMRI

Abstract

In fMRI research, one often aims to examine activation in specific functional regions of interest (fROIs). Current statistical methods tend to localize fROIs inconsistently, focusing on avoiding detection of false activation. Not missing true activation is however equally important in this context. In this study, we explored the potential of an alternative-based thresholding (ABT) procedure, where evidence against the null hypothesis of no effect and evidence against a prespecified alternative hypothesis is measured to control both false positives and false negatives directly. The procedure was validated in the context of localizer tasks on simulated brain images and using a real data set of 100 runs per subject. Voxels categorized as active with ABT can be confidently included in the definition of the fROI, while inactive voxels can be confidently excluded. Additionally, the ABT method complements classic null hypothesis significance testing with valuable information by making a distinction between voxels that show evidence against both the null and alternative and voxels for which the alternative hypothesis cannot be rejected despite lack of evidence against the null.

Examining overlap in behavioral and neural representations of morals, facts, and preferences.

“…We used this arbitrary threshold was so that our results could be easily compared with prior work, which has used the same parameters (Dodell-Feder et al, 2011; Koster-Hale et al, 2013; Saxe & Kanwisher, 2003; Young et al, 2007, 2010, 2011); however, we also wanted to ensure that our findings were not dependent on it. How best to balance Type I and Type II error when selecting functional ROIs is an open question (Degryse et al, 2017), so we selected ROIs based on the peak coordinates from a whole brain random effects contrast (belief > photograph) across all participants, and replicated the central analyses (see supplemental analyses in the online supplemental materials; for peak coordinates, see Table S3 of the online supplemental materials). The results of this analysis are identical to the reported ROI analyses (Figure S2 of the online supplemental materials).…”

Weight Loss by Low-Calorie Diet Versus Gastric Bypass Surgery in People With Diabetes Results in Divergent Brain Activation Patterns: A Functional MRI Study

“…Most of our ROIs were functionally defined since many areas that are described as relevant to food cue responsivity, such as the dorsolateral prefrontal cortex (dlPFC), are not accurately defined as distinct anatomical areas in the brain and may either encompass two or more anatomical regions or be a subpart of a larger anatomical region. In addition, functional definitions are often considered superior to anatomical with regard to intersubject variability ( 19 , 20 ). To avoid biases, all the functional ROIs for the food task were independently defined on the basis of the group mean effect of the task in all participants in the contrast all stimuli great than baseline.…”

Weight Loss by Low-Calorie Diet Versus Gastric Bypass Surgery in People With Diabetes Results in Divergent Brain Activation Patterns: A Functional MRI Study

“…Most of our ROIs were functionally defined since many areas that are described as relevant to food cue responsivity, such as the dlPFC, are not accurately defined as distinct anatomical areas in the brain, and may either encompass two or more anatomical regions, or be a sub-part of a larger anatomical region. In addition, functional definitions are often considered superior to anatomical with regards to inter-subject variability (19,20). To avoid biases, all the functional ROIs for the food task were independently defined based on the group mean effect of the task in all participants in the contrast "all stimuli > baseline".…”