Miyamoto Jun J, Honda Manabu, Saito Daisuke N, Okada Tomohisa, Ono Takashi, Ohyama Kimie, Sadato Norihiro
Division of Cerebral Integration, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
Cereb Cortex. 2006 May;16(5):669-75. doi: 10.1093/cercor/bhj012. Epub 2005 Aug 3.
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.
牙齿的触觉感受参与了多种口腔功能，如咀嚼和言语。我们使用功能磁共振成像技术研究了包括牙齿在内的口腔区域的皮质感觉表征。首先，我们确定了中央后回（GpoC）中嘴唇、牙齿和舌头的躯体定位表征。对下唇、舌头和牙齿施加触觉刺激。每个刺激激活的焦点通过激活区域的重心（COG）来表征。其次，我们根据每种感觉表征之间的重叠情况，研究了GPoC中躯体定位组织的前后变化。在GPoC的前部，牙齿表征的COG明显位于舌头表征的COG上方，嘴唇表征的COG下方，这与Penfield提出的经典“感觉小人”一致；然而，这种躯体定位表征在GPoC的中部和后部变得不清晰。GPoC中部和后部各表征之间的重叠明显大于GPoC前部。这些发现支持了这样一种理论，即来自口腔结构的输入在初级躯体感觉皮层中分层汇聚。
