Somatotopic representation of laryngeal and supralaryngeal articulatory movements in the sensorimotor cortex
Résumé
Since Penfield's seminal work on electrocortical stimulation, brain imaging studies have confirmed a general somatotopic functional organization related to parts of the human body in the sensorimotor cortex. However, few studies have investigated the possibility to discriminate distinct representation sites of laryngeal and supralaryngeal articulations. In the present study, we used functional magnetic resonance imaging to further test a possible somatotopic organization of larynx, lip, jaw and tongue articulatory movements. In order to minimize movement-related imaging artifacts, a sparse sampling acquisition technique was used, where the motor task occurred during a silent interval between successive image acquisitions. To delimitate cerebral activations specific to supralaryngeal articulations, we had participants perform independently lip protrusion, jaw lowering and tongue retroflex movements. Additionally, for laryngeal activities, we looked for cerebral activation corresponding to the production of the /i/ vowel. For all movements, a group analysis revealed strong bilateral activations within the sensorimotor cortex as well as within the supplementary motor area and the anterior cingulate gyrus, the inferior frontal gyrus, the insula, the inferior parietal lobule, the putamen, the thalamus and the cerebellum. At the individual level, a dorso-ventral bilateral somatotopic organization of lip, jaw, larynx and tongue articulators, respectively, was detectable in the sensorimotor cortex and could be spatially discriminated for the great majority of the participants. The individually proven possibility to differentiate the sensorimotor representation sites of lip, jaw, larynx and tongue movements is of particular interest for studies investigating speech motor control and disorders as well as cortical plasticity after neurosurgery.