Cerebral Cortex Advance Access originally published online on August 3, 2005
Cerebral Cortex 2006 16(5):669-675; doi:10.1093/cercor/bhj012
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The Representation of the Human Oral Area in the Somatosensory Cortex: a Functional MRI Study
1 Division of Cerebral Integration, National Institute for Physiological Sciences, Okazaki 444-8585, Japan, 2 Maxillofacial Orthognathics, Graduate School, Tokyo Medical and Dental University, Tokyo 113-8549, Japan, 3 SORST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan, 4 RISTEX, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan and 5 Department of Functional Neuroimaging, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan
Address correspondence to Norihiro Sadato, Division of Cerebral Integration, National Institute for Physiological Sciences, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan. Email: sadato{at}nips.ac.jp.
The tactile sensation of the teeth is involved in various oral functions, such as mastication and speech. Using functional magnetic resonance imaging, we investigated the cortical sensory representation of the oral area, including the teeth. First, we identified the somatotopic representation of the lips, teeth and tongue in the postcentral gyrus (GpoC). Tactile stimuli were applied to the lower lip, tongue and teeth. The foci activated by each stimulus were characterized by the center of gravity (COG) of activated areas. Secondly, we examined the rostro-caudal changes in the somatotopic organization in the GPoC in terms of the overlap between each sensory representation. In the rostral portion of the GPoC, the COG of the representation of teeth was located significantly superior to that of the tongue and inferior to that of the lip, consistent with the classical ‘sensory homunculus’ proposed by Penfield; however, this somatotopic representation became unclear in the middle and caudal portions of the GPoC. The overlap between each representation in the middle and caudal portions of the GPoC was significantly greater than that in the rostral portion of the GPoC. These findings support the theory that the input from oral structures converges hierarchically across the primary somatosensory cortex.
Key Words: fMRI • oral area • postcentral gyrus • somatosensory cortex • teeth representation
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