Cerebral Cortex Advance Access originally published online on July 25, 2007
Cerebral Cortex 2008 18(4):837-845; doi:10.1093/cercor/bhm131
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A Larynx Area in the Human Motor Cortex
1 Department of Psychology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6, 2 Department of Psychiatry, University of British Columbia, Vancouver, BC V6T 2A1 Canada
Address correspondence to Steven Brown, PhD, Department of Psychology, Simon Fraser University, Robert C. Brown Hall, 8888 University Drive, Burnaby, BC, Canada, V5A 1S6. Email: stebro{at}sfu.ca.
The map of the human motor cortex has lacked a representation for the intrinsic musculature of the larynx ever since the electrical stimulation studies of Penfield. In addition, there has been no attempt to localize this area using neuroimaging techniques. Because of the central importance of laryngeal function to vocalization, we sought to localize an area controlling the intrinsic muscles of the larynx by using functional magnetic resonance imaging and to place this area in a somatotopic context. We had subjects perform a series of oral tasks designed to isolate elementary components of phonation and articulation, including vocalization of a vowel, lip movement, and tongue movement. In addition, and for the first time in a neuroimaging study, we had subjects perform "glottal stops," in other words forced closure of the glottis in the absence of vocalizing. The results demonstrated a larynx-specific area in the motor cortex that is activated comparably by vocal and nonvocal laryngeal tasks. Converging evidence suggests that this area is the principal vocal center of the human motor cortex. Finally, the location of this larynx area is strikingly different from that reported in the monkey. We discuss the implications of this observation for the evolution of vocal communication in humans.
Key Words: fMRI • larynx • motor • phonation • speech • vocalization