Generating facial expressions of disgust activates neurons in the thoracic spinal cord: a spinal fMRI study.

Facial expressions of disgust, which involve movement of the levator labii muscles on the nose, allow an organism to restrict the intake of potentially aversive stimuli by constricting the air cavities in the nostrils and reducing the speed of air intake. In the current research, we used fMRI of the thoracic spinal cord to measure neural activity related to (1) the contraction of the intercostal muscles that modulate the velocity of air intake and (2) the sensory feedback associated with this contraction. Thirteen participants completed two spinal fMRI runs in which the thoracic segments of the spinal cord were measured. Each five-minute 40-second run consisted of three 60-second blocks in which participants repeatedly generated a disgusted facial expression or a non-emotional expression consisting of repeated stretching of the lips (which did not involve the nasal cavity). Forty-second rest blocks were interleaved between each expression block. The results demonstrated that generating emotional expressions of disgust produces significantly more activity than producing non-emotional facial expressions. This activity occurred in both ventral (motoric) and dorsal (sensory) regions of the upper segments of the thoracic spinal cord and demonstrates a link between the generation of facial expressions and embodied emotional responses.