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Emotional facial expressions convey a wealth of non-verbal information, including an individual’s mood, state of mind and intention, making them critically important for social communication. While viewing emotional expressions evokes an enhanced neural response in the amygdala and throughout the visual cortex, including the primary visual cortex (V1), the effect of facial valence (emotional content of the face) in V1 is surprising as the early visual cortex is not typically thought to process emotional aspects from stimuli. In a recent study published in Nature Communications, Jason Fu, SOM Class of 2025, helped uncover the functional pathways by which emotional information is transmitted from the amygdala to V1.

“Researching these neural circuits involving emotional processing is important for understanding how primate brains evolved to manage the complexities involved with large social groups,” said Fu, who conducted the research during a post-bachelor’s research fellowship at the National Institute of Mental Health of the NIH. “We know a lot about the feedforward processing pathway from V1 to other brain regions, but we know little about feedback pathways from those regions back to V1. Utilizing laminar-resolution functional MRI (7T fMRI), our experiment aimed to understand the feedback responses from the amygdala to V1, and its role in enhancing the processing of visual features associated with emotional stimuli.”

The study team applied a novel MRI technique called vascular space occupancy (VASO) to measure cerebral blood volume across cortical layers, which enabled layer-specific measurements of both feedforward and feedback activity in V1 and minimized confounds introduced by draining veins that are inherent to conventional blood-oxygen-level-dependent (BOLD) fMRI.

“We found that facial valence sensitivity was most pronounced in superficial cortical layers of V1 and was not restricted to the retinotopic location of the stimuli, consistent with direct and diffuse feedback-like projections from the amygdala. Together, our results provide a feedback mechanism by which the amygdala directly modulates activity at the earliest stage of visual processing,” said Fu.

As for the next steps, Fu says, “While our stimuli set consisted of faces with neutral, fearful or happy expressions, very rarely do people interact with uniformly cropped and grayscale human faces. Substituting these faces for more natural scenes that evoke neutral, happy or fearful emotions could be a more ecologically valid approach. Future studies can utilize network analysis to examine whole-brain dynamics and incorporate different imaging modalities to better understand whether the widespread valence effects across the visual cortex are due to direct influence from the amygdala, feedforward inputs from V1, or a combination of both.”