A Rapid Subcortical Amygdala Route for Faces Irrespective of Spatial Frequency and Emotion

Abstract

There is significant controversy over the anatomical existence and potential function of a direct subcortical visual pathway to the amygdala. It is thought that this pathway rapidly transmits low spatial frequency information to the amygdala independently of the cortex and yet this function has never been causally determined. In this study, neural activity was measured using magnetoencephalography (MEG) while participants discriminated the gender of neutral and fearful faces filtered for low or high spatial frequencies. Dynamic causal modelling (DCM) revealed that the most likely underlying neural network consisted of a subcortical pulvino-amygdala connection that was not modulated by spatial frequency or emotion and a cortico-amygdala connection that conveyed predominantly high spatial frequencies. Crucially, data-driven neural simulations demonstrated a clear temporal advantage of the subcortical route (70ms) over the cortical route (155ms) in influencing amygdala activity. Thus, our findings support the existence of a rapid functional subcortical pathway that is unselective of the spatial frequency or emotional content of faces.