Disrupting the Right Inferior Frontal Gyrus Increases Social Brain Activity During Emotion Recognition

Neuroimaging studies have identified a specialised social brain network that supports emotion recognition and social cognition. This network performs a range of functions that include facial expression recognition and inferring the mental states of others. Studies of neuropsychological patients report that damage to the right inferior frontal gyrus (IFG), the top-down control area in this network, impairs facial expression recognition. To investigate how transient disruption of the right IFG affects the wider social brain we combined transcranial magnetic stimulation (TMS) with functional magnetic resonance imaging (fMRI). Participants (n=20) were scanned across two sessions while performing a delayed match-to-sample emotion recognition task in which happy or fearful expressions were preceded by a congruent or incongruent word cue. Prior to each scan, thetaburst TMS was delivered over the right IFG or over the vertex control site (session order was balanced across participants). A group whole-brain analysis revealed that TMS to the IFG increased neural activity in multiple regions of the social brain network. These included the bilateral temporal pole, precuneus and medial prefrontal cortex (mPFC). This pattern of results shows that the disruption of top-down control mechanisms localised in the IFG alters the neural processing in remote nodes of the social brain network. Our findings are discussed within the wider context of how we recognise and understand the emotions of other people.