MODULATION EFFECT OF MOTOR ACTIVITY ON LIMBIC AREAS: AN FMRI STUDY

Abstract

Neural activation of the motor cortex has been consistently reported to be evoked in the emotion processing of facial expressions, but it is poorly understood whether and how the motor system influences the activity of limbic areas during participants’ perceived emotional expressions. In this study, we proposed that motor activations evoked by emotional processing influence the activations in limbic areas such as amygdala during the perception of facial expressions. To examine this issue, a masked priming paradigm was adopted in our fMRI experiment, which could modulate the activation within the motor cortex when healthy participants perceived sad or happy facial expressions. We found that the first presented stimulus (masked prime) in each trial reduced the activations in the premotor cortex and inferior frontal gyrus when the movement of facial muscles implied by the arrows on the prime stimulus was consistent with that implied by the target face expressions (compatible condition), but increased the activations in these two areas when the movements implied by the arrows and the target face expressions were inconsistent (incompatible condition). The superior temporal gyrus, middle cingulate gyrus and amygdala also showed similar response tendency to that in motor cortex. Moreover, psychophysiological interaction (PPI) analysis showed that both right middle cingulate gyrus and bilateral superior temporal gyrus were closely linked to the premotor cortex with inferior frontal gyrus during the incompatible trials compared with the compatible trials. Together with this result and the significant activation correlations between the motor cortex and the limbic areas, this work revealed the modulation effect of motor cortex on brain regions related to emotion perception, suggesting that motor representation of facial movements can affect emotion experience. Our results provide new evidence for the functional role of motor system in the perception of facial emotions, and could contribute to the understanding of the deficit in social interaction for patients with autism or schizophrenia.