Transcranial magnetic stimulation modulates left premotor cortex activity in facial expression recognition as a function of anxiety level

Abstract

Recognition of emotional facial expressions is based on simulation and mirroring processes, and the premotor cortex is supposed to support this simulation mechanism. The role of this prefrontal area in processing emotional faces with different valence (anger, fear, happiness and neutral) was explored taking into account the effect of the lateralization model (more right-side activation for negative emotions; more left-side activation for positive emotions) of face processing and anxiety level (high vs low). High-frequency repetitive transcranial magnetic stimulation (rTMS, 10 Hz) was applied to the left prefrontal area to induce an increased activation response within the left premotor cortex. Twenty-nine subjects, who were divided into two different groups depending on their anxiety level (high/low anxiety; State-Trait-Anxiety Inventory (STAI), were asked to detect emotion / no emotion. Accuracy (AcI) and response times (RTs) were considered in response to the experimental conditions. A general significant increased performance was found in response to positive emotions in the case of left-side stimulation. Moreover, whereas high-anxiety subjects revealed a significant negative-valence bias in absence of stimulation, they showed a more significant AcI increasing and RTs decreasing in response to positive emotions in case of left premotor brain activation. The present results highlight the role of the premotor system for facial expression processing as a function of emotional type, supporting the existence of a valence-specific lateralized system within the prefrontal area. Finally, a sort of "restoring effect" induced by TMS was suggested for high-anxiety subjects.

Face Processing and TMS

“…It also depends on somatosensory and motor areas that internally simulate the observed emotion, and that this process aids expression recognition (Niedenthal, 2007). This has been causally demonstrated in TMS studies that delivered TMS over the left premotor cortex (Enticott et al, 2008, Balconi et al, 2014. Rochas et al (2013) also reported that TMS delivered over the left presupplementary motor area (pre-SMA) selectively impaired the recognition of happy faces but not fearful or angry faces.…”

“…This is, at least partly, because many of the brain areas involved in processing expressions are located on the lateral brain surface and can be directly stimulated with TMS. TMS studies of expression processing have targeted the OFA (Pitcher et al, 2008), the posterior STS (Pourtois et al, 2004, Sliwinska and Pitcher, 2018, Sliwinska et al, 2020b, premotor cortex (Balconi et al, 2014), the face area in the somatosensory cortex (Pitcher et al, 2008), medial prefrontal cortex (Mattavelli et al, 2013), dorsolateral prefrontal cortex (Zwanzger et al, 2014) and the cerebellum (Ferrari et al, 2018). The fact that expressions are processed across so many areas distributed across the brain demonstrates the saliency of the face when conveying emotion.…”