Department of Anatomy and Histology, University of Sydney, Sydney, NSW 2006, Australia School of Medicine, University of Western Sydney, Sydney, NSW 1797, Australia Jaw Function and Orofacial Pain Research Unit, Faculty of Dentistry, University of Sydney, NSW 2006, Australia.
Pain. 2010 Nov;151(2):384-393. doi: 10.1016/j.pain.2010.07.027. Epub 2010 Aug 21.
The conscious perception of somatosensory stimuli is thought to be located in the contralateral cerebral cortex. However, recent human brain imaging investigations in the spinal system report bilateral primary somatosensory cortex (SI) activations during unilateral noxious stimuli and that this ipsilateral spinal representation may be independent of transcallosal connections. In the trigeminal system, there is primate evidence for an ipsilateral somatosensory pathway through the thalamus to the face SI. However, the organization of the trigeminal nociceptive pathway in the human is not clear. The aim of this study was to determine whether noxious stimuli applied to the face are transmitted to the cerebral cortex by bilateral pathways. We used functional magnetic resonance imaging (fMRI) to compare ipsilateral and contralateral activation of the thalamus, SI and secondary somatosensory cortex (SII) during muscle and cutaneous orofacial pain and innocuous facial stimulation in healthy human subjects. We found that both muscle and cutaneous noxious stimuli, from injections of hypertonic saline into the right masseter or overlying skin, evoked bilateral increases in signal intensity in the region encompassing the ventral posterior thalamus as well as the face region of SI and SII. In contrast, innocuous unilateral brushing of the lower lip evoked a strict contralateral ventroposterior thalamic activation, but bilateral activation of SI and SII. These data indicate that, in contrast to innocuous inputs from the face, noxious information ascends bilaterally to the face SI through the ventroposterior thalamus in humans.
躯体感觉刺激的意识感知被认为位于对侧大脑皮层。然而，最近对脊髓系统的人类脑成像研究报告称，在单侧有害刺激时双侧初级躯体感觉皮层（SI）被激活，并且这种同侧脊髓表示可能独立于胼胝体连接。在三叉神经系统中，有灵长类动物的证据表明存在通过丘脑到面部 SI 的同侧躯体感觉通路。然而，人类三叉神经痛觉通路的组织尚不清楚。本研究旨在确定面部的有害刺激是否通过双侧通路传递到大脑皮层。我们使用功能磁共振成像（fMRI）来比较肌肉和皮肤口腔面部疼痛以及无害面部刺激期间，双侧丘脑、SI 和次级躯体感觉皮层（SII）的同侧和对侧激活。我们发现，来自右咬肌或上覆皮肤的高渗盐水注射的肌肉和皮肤有害刺激都引起了包含腹后丘脑以及 SI 和 SII 的面部区域在内的区域的信号强度的双侧增加。相比之下，无害的单侧下唇刷刺激仅引起严格的对侧腹后丘脑激活，但同侧 SI 和 SII 的激活。这些数据表明，与来自面部的无害输入相反，在人类中，有害信息通过腹后丘脑双侧上升到面部 SI。
