False positive rates in Voxel-based Morphometry studies of the human brain: Should we be worried?. (May 2015)

• Record Type: Journal Article
• Authors: Scarpazza, Cristina; Tognin, Stefania; Frisciata, Silvia; Sartori, Giuseppe; Mechelli, Andrea
• Is Part Of: Neuroscience and biobehavioral reviews. Volume 52(2015:May)
• Page Start: 49
• Page End: 55
• Publication Date: 2015-05
• Subjects: Neuroimaging -- Voxel-based Morphometry -- False positive rate -- Unbalanced design -- Balanced design; Psychophysiology -- Periodicals; Human behavior -- Periodicals; Animal behavior -- Periodicals; Neurology -- Periodicals; Behavior -- Periodicals; Ethology -- Periodicals; Neurology -- Periodicals; Psychophysiologie -- Périodiques; Comportement humain -- Périodiques; Animaux -- Mœurs et comportement -- Périodiques; Neurologie -- Périodiques; Animal behavior; Human behavior; Neurology; Psychophysiology; Periodicals; Electronic journals; 573.8
• DOI: 10.1016/j.neubiorev.2015.02.008
• Languages: English
• ISSNs: 0149-7634

Abstract

Highlights: Methodological factors influencing the results of a VBM study are reviewed. VBM with balanced designs is not vulnerable to high false positive rate. Sample size, smoothing and modulation do not influence false positive rate. False positives are mainly located in the neocortex, in particular the frontal lobe. These results were replicated in two independent datasets. Abstract: Voxel-based Morphometry (VBM) is a widely used automated technique for the analysis of neuroanatomical images. Despite its popularity within the neuroimaging community, there are outstanding concerns about its potential susceptibility to false positive findings. Here we review the main methodological factors that are known to influence the results of VBM studies comparing two groups of subjects. We then use two large, open-access data sets to empirically estimate false positive rates and how these depend on sample size, degree of smoothing and modulation. Our review and investigation provide three main results: (i) when groups of equal size are compared false positive rate is not higher than expected, i.e. about 5%; (ii) the sample size, degree of smoothing and modulation do not appear to influence false positive rate; (iii) when they exist, false positive findings are randomly distributed across the brain. These results provide reassurance that VBM studies comparing groups are not vulnerable to the higher than expected false positive rates that are evident in single case VBM.