Common and distinct neural representations of social and non-social disgust in the brain: An ALE meta-analysis and MACM analysis

During the past two decades several brain imaging studies have examined the neural correlates of disgust (the first study employing functional MRI was published by Phillips et al. (Phillips et al., 1997)). These studies usually combined the presentation of disgust-associated stimuli during neuroimaging acquisition and examined associated increases in regional brain activity. However, the original studies reported a number of different brain regions and it is still a matter of debate which regions may underlie disgust processing. On the one hand characteristics of the original studies such as low sample size, lack of power and robustness or differences in the recruited samples may have contributed to the inconsistent findings. On the other hand, differences in the employed stimuli may account for the inconsistent results. Among the previous studies, different kinds of stimuli have been employed, which could be classified into two main domains. The first domain contains facial expressions of disgust and film clips (also, static and dynamic disgust facial expressions) depicting disgusted facial expressions on the basis of their ability to evoke a vicarious experience of disgust, the second domain includes generally disgust-inducing pictures and film clips (also, static and dynamic disgust elicitors) which can evoke strong disgust-related feelings. The static and dynamic disgusted facial expressions carry strong socially communicative and interpersonal meaning and convey the experience of disgust of the depicted person to the observer whereas the disgusting stimuli induce directly a disgusting experience in the observer. It is therefore conceivable that the stimuli which vary along a social dimension (non-social, direct disgust inducing stimuli vs social communicative and interpersonal disgust stimuli) may induce differential as well as common neural activity. Despite a large number of disgust-related fMRI studies there is to our knowledge not a single neuroimaging meta-analysis that capitalized on the previous original studies to robustly determine the neural correlates of disgust processing or differences between the social and non-social disgust stimuli. To this end the present activation likelihood estimation (ALE) meta-analysis aims at investigating brain regions engaged during disgust processing in healthy subjects and to determine common and distinct neural correlates along the social and non-social dimensions. The ALE meta-analysis approach is not limited by experimental design, paradigm, task, number of subjects and data analysis methods (Eickhoff, Bzdok, Laird, Kurth, & Fox, 2012; Laird et al., 2005; Wager, Lindquist, & Kaplan, 2007), thus allowing general inferences to be drawn, which can help to resolve previous inconsistencies in the literature.