Unraveling the morphological brain architecture of human aggression: A systematic review and meta-analysis of structural neuroimaging studies

Aggression is an umbrella term referring to behaviors intended to harm others. However, aggressive behaviors vary in terms of forms (i.e., physical, verbal) and functions (i.e., proactive, reactive). Recent findings suggest that both motives and forms may be associated with distinct brain structures. However, no studies have metaanalytically summarized their commonalities and differences. A systematic search strategy was conducted up to May 1st 2023 using PubMed, Google Scholar, and Web of Science. Seed-based d Mapping with Permutation of Subject Image was used to meta-analyze voxel-based morphometry studies. Exploratory analyses on metaanalytic findings were conducted to identify their associated mental functions and examine their degree of overlap with brain lesion associated with aggression. A total of 92 experiments were included in the metaanalysis (N=2593, mean age=26.2, 68.5% males). General aggression was characterized by reduced grey matter volume (GMV) in the medial prefrontal cortex. Reactive aggression was associated with reduced GMV in the rostral medial prefrontal cortex, and bilateral superior temporal gyrus, and proactive aggression with greater GMV in the ventral caudate. Co-activation brain networks of these morphological correlates further distinguished reactive and proactive into socio-affective/somatosensory and motivational processes, respectively. We also found that the medial prefrontal cortex cluster of general aggression was a primary site in which focal brain lesion may increase the risk for aggression. The current study highlight that functions of aggression are associated with distinct abnormalities in grey matter volume. These findings add to the growing body of literature suggesting potentially distinct aetiologies between aggression motives.