Inside the wire: aggression and functional interhemispheric connectivity in the human brain

An aggressive personality style has been proposed to arise from a cortical asymmetry between the left and right frontal hemispheres. In the present transcranial magnetic stimulation (TMS) study, evidence was sought for a link between an aggressive personality style and functional interhemispheric connectivity between the left and right frontal cortices. Functional interhemispheric connectivity was measured by determining transcallosal inhibition (TCI) using TMS in 20 healthy right-handed volunteers, who were given the Buss-Perry Aggression Questionnaire (AQ) and a selective attention task. Analyses showed higher levels of left-to-right TCI significantly correlated with higher AQ scores. Furthermore, increased left-to-right together with reduced right-to-left TCI was associated with a stronger attentional bias for angry faces. This is the first study to provide a biological mechanism underlying the asymmetry between left and right frontal cortex activity in human aggression. We conclude that an aggressive personality style and selective attention to angry faces are positively correlated with functional interhemispheric connectivity.