Somatotopy of the extrinsic laryngeal muscles in the human sensorimotor cortex

The larynx is the major organ of vocalization. The intrinsic laryngeal muscles modify the internal shape of the larynx while the extrinsic laryngeal muscles move the entire larynx vertically in the airway. Previous neuroimaging research has established the somatotopic location of the intrinsic musculature of the larynx in the human motor cortex and showed it to be in an evolutionarily novel location compared to the homologous region in monkey cortex. In the current study, we attempted for the first time to determine the somatotopic localization of the extrinsic laryngeal musculature in humans. In a functional magnetic resonance imaging experiment, we had participants voluntarily move their larynx upward and/or downward in the airway in the absence of vocalization to engage the extrinsic laryngeal muscles or vocalize in the absence of vertical laryngeal movement to engage the intrinsic laryngeal muscles. Vertical movement of the larynx activated ventral pericentral sensorimotor cortex extending dorsally to overlap with the representation of the intrinsic laryngeal muscles. This pattern is a reversal from the somatotopy of the monkey, where the extrinsic laryngeal muscles are represented dorsally to the intrinsic laryngeal muscles.