健康成人戴用软垫紧咬运动时脑激活区域的功能性磁共振成像研究

目的　应用功能性磁共振成像技术探讨戴软垫紧咬运动时人脑功能活动区域定位,试图从中枢机制探 讨垫的治疗作用机理。方法　选取10名健康成人受试者,采用时段设计,任务状态与休息状态交替。任务状态 分2组设计,实验组为戴软垫紧咬运动,对照组为不戴软垫紧咬运动。采用Elscint/GE 2.0T磁共振系统成像, 应用SPM99软件进行数据后处理及组分析。结果　实验组10名受试者在单侧或双侧的运动皮层、感觉皮层、前额 叶皮层、颞叶皮层、前运动皮层、脑岛、额盖、基底神经节壳核、顶叶皮层及扣带回等区域有明显激活。组分析结果 显示双侧运动皮层(BA6)、右侧感觉皮层、双侧基底神经节壳核、双侧脑岛等区域均出现明显激活,其中左侧运动皮 层的激活程度明显强于右侧。对照组紧咬运动组分析结果显示双侧运动皮层(BA6)、双侧感觉皮层、双侧基底神经 节壳核、左侧顶叶皮层等区域均出现明显激活,其中运动皮层的激活双侧基本对称。结论　戴软垫后紧咬运动 脑皮层激活区域尤其是运动皮层和感觉皮层的变化可能是垫作用机理的中枢机制。     

健康成人戴用软(牙合)垫紧咬运动时脑激活区域的功能性磁共振成像研究

目的　应用功能性磁共振成像技术探讨戴软垫紧咬运动时人脑功能活动区域定位,试图从中枢机制探 讨垫的治疗作用机理。方法　选取10名健康成人受试者,采用时段设计,任务状态与休息状态交替。任务状态 分2组设计,实验组为戴软垫紧咬运动,对照组为不戴软垫紧咬运动。采用Elscint GE2.0T磁共振系统成像, 应用SPM99软件进行数据后处理及组分析。结果　实验组10名受试者在单侧或双侧的运动皮层、感觉皮层、前额 叶皮层、颞叶皮层、前运动皮层、脑岛、额盖、基底神经节壳核、顶叶皮层及扣带回等区域有明显激活。组分析结果 显示双侧运动皮层(BA6)、右侧感觉皮层、双侧基底神经节壳核、双侧脑岛等区域均出现明显激活,其中左侧运动皮 层的激活程度明显强于右侧。对照组紧咬运动组分析结果显示双侧运动皮层(BA6)、双侧感觉皮层、双侧基底神经 节壳核、左侧顶叶皮层等区域均出现明显激活,其中运动皮层的激活双侧基本对称。结论　戴软垫后紧咬运动 脑皮层激活区域尤其是运动皮层和感觉皮层的变化可能是垫作用机理的中枢机制。     

Cortical activation resulting from painless vibrotactile dental stimulation measured by functional magnetic resonance imaging (FMRI)

There have been few investigations on hemodynamic responses in the human cortex resulting from dental stimulation. Identification of cortical areas involved in stimulus perception may offer new targets for pain treatment. This initial study aimed at establishing a cortical map of dental representation, based on non-invasive fMRI measurements. Five right-handed subjects were studied. Eight maxillary and 8 mandibular teeth were stimulated after the vibratory perception threshold was determined for each tooth. Suprathreshold stimulation was repeated thrice per session, in a total of three sessions performed on three consecutive days. Statistical inference on cluster level identified increased blood-oxygen-level-dependent signal during vibratory dental stimulation, primarily in the insular cortex bilaterally and in the supplementary motor cortex. No significant brain activation was observed in the somatosensory cortex with this stimulation protocol. These results agree with previous findings obtained from invasive direct electrical cortical stimulation of the human insula.     

Neuroplasticity of edentulous patients with implant-supported full dentures

Edentulous patients with implant-supported prostheses report improved tactile discriminative capabilities and motor function compared with when they wore complete dentures. 'Osseoperception' is defined as the ability to identify kinesthetic sensation without the input from periodontal mechanoreceptors. This sensation is generated from the temporomandibular joint, masticatory muscle, mucosa, and periosteum, and provides sensory and motor information related to mandible movements and occlusion. The aim of this study was to analyze the cortical plasticity occurring in patients with implant-supported prostheses. Twenty edentulous patients with implant-supported full dentures or traditional complete dentures were recruited for a clenching task. They were scanned by functional magnetic resonance imaging (fMRI), and the data were analyzed using the spm99 software package to generate activation brain maps. Increased blood oxygen level dependent signals in the primary sensorimotor cortex were found in patients with implant-supported fixed dentures. Other activated areas included prefrontal cortex, Broca's area, premotor cortex, supplementary motor area, superior temporal gyrus, insular, basal ganglion, and hippocampus. We suggest that sensory and motor feedback to the central nervous system can be restored by implant-supported full dentures. Activation of the primary sensorimotor cortex in patients with implant-supported dentures might explain the improved tactile, stereognostic ability, and mastication functions, which are more similar to the natural dentition.     

Functional magnetic resonance imaging of human jaw movements

This study used functional magnetic resonance images (fMRI) to examine brain activity during clenching, gum chewing, and tapping tasks. It has been considered difficult to obtain sufficient fMRI data during jaw movement because the head motion associated with the jaw movements creates artifacts on the images. To avoid these artifacts, larger pixels were used, thus allowing some head motion of the subjects, and data from subjects where the heads were evaluated to have moved more than 0.5 mm were discarded. Further, all pixels obtained by fMRI were evaluated and pixels positively synchronized with the task, which were considered to show brain activity, were selected. Sufficient fMRI data was obtained from 30 experiments, 10 sets for each task. During the clenching and tapping tasks, the activated pixels were in the sensory, motor and pre-motor cortexes, and in the sensory and motor cortexes but not in the pre-motor cortex during the gum chewing task. There appears to be no significant differences between right- and left-hemispheres. It is conceivable that there are differences between voluntary jaw movements (clenching and tapping tasks) and mastication (gum chewing task) concerning the control of jaw movements.     

Analysis of brain activity during clenching by fMRI

It has been considered difficult to obtain satisfactory functional magnetic resonance images (fMRI) during jaw movements because the head motion during jaw movements makes artefacts on the images. To avoid these artefacts, we chose clenching task and larger pixels to allow some head motion of the subjects. Further the study discarded all data from subjects whom the head was evaluated to move more than 0.3 mm. The study examined 10 healthy right-handed volunteers with echo-planar magnetic resonance (MR) imaging and functional MR signal intensity changes could be obtained in all subjects. However, in the analysis of each pixel of individuals, three different types of pixels were established. It was determined that the pixels that synchronized positively with the task on/off and where signal intensity increase was below 10% expressed the real brain activity. Pixels showing the real brain activity were found in the sensory, motor and pre-motor cortexes in both hemispheres in all subjects, and also in the insula region of two subjects. No pixels were found in the striatum and supplementary motor areas. From the above careful consideration and individual analysis of each pixel, it was concluded that brain activity during the clenching task could be obtained by fMRI.     

Cortical representation area of human dental pulp

To elucidate the dental pulp-representing area in the human primary somatosensory cortex and the presence of A-beta fibers in dental pulp, we recorded somatosensory-evoked magnetic fields from the cortex in seven healthy persons using magnetoencephalography. Following non-painful electrical stimulation of the right maxillary first premolar dental pulp, short latency (27 ms) cortical responses on the magnetic waveforms were observed. However, no response was seen when stimulation was applied to pulpless teeth, such as devitalized teeth. The current source generating the early component of the magnetic fields was located anterior-inferiorly compared with the locations for the hand area in the primary somatosensory cortex. These results demonstrate the dental pulp representation area in the primary somatosensory cortex, and that it receives input from intradental A-beta neurons, providing a detailed organizational map of the orofacial area, by adding dental pulp to the classic "sensory homunculus".     

疼痛性冷刺激和非痛温热刺激口腔时对大脑皮层反应强度的影响

目的 探索疼痛性冷刺激和非痛温热刺激口腔时对大脑皮层反应强度的影响。方法 选取6名健康志愿者,采用组块设计方法,利用水传递装置分别用冷水（4 ℃）和温水（23 ℃）刺激其口腔,采集全脑血氧水平依赖对比的功能性磁共振成像（fMRI）扫描数据进行分析。结果 冷水和温水刺激共同激活了左侧中央前后回、岛叶/岛盖、前扣带回（ACC）、眶额皮层,右侧中脑红核和丘脑。此外,冷水刺激还激活了左侧枕叶、运动前皮层布罗德曼分区（BA）6、右侧BA44、舌回,以及顶叶BA7和BA40,初级躯体感觉皮层SⅠ。疼痛性冷水刺激激活的脑区多于无痛温水,而激活脑区的强度小于温水,但是疼痛冷水刺激在ACC的激活强度明显大于无痛温水刺激。结论 大脑皮层对疼痛性冷刺激口腔时反应的脑区的激活强度小于非痛性温热水刺激,但是ACC脑区的激活强度大于非痛性温水刺激。     

Cortical mechanism of oral somatosensory function

Somatosensory information from the orofacial area is received by peripheral sensory neurons and then projected into the primary somatosensory cortex. Within the classical sensory homunculus, the primary somatosensory cortex incorporates a somatotopic functional organization. The sensory-representing area for the oral region is relatively widely distributed, and given its size in comparison with that for the rest of the human body, this indicates great importance for oral function in human. Non-invasive neuroimaging tools have allowed us to clarify the exact locations and response times of cortical neurons following oral sensory stimulation. Here, we describe a detailed organizational map of the orofacial structure-representing areas in the human cerebral cortex.     

Comparison of brain activation via tooth stimulation

The aim of this study was to evaluate the sensation of each tooth type at the cortical level. The tactical sensation from teeth plays an important role in controlling the masticatory system. However, the role of each tooth type has not been determined. Functional near-infrared spectroscopy (fNIRS) was used to detect changes in cerebral blood flow in the somatosensory cortex of 12 healthy volunteers. Painless vibrotactile stimuli were applied to 8 teeth (left maxillary and mandibular incisors, canines, 1(st) premolars, or 1(st) molars). The somatosensory cortex was activated during stimulation of all teeth. A comparison of cortical activation revealed significantly greater activation during stimulation of the maxillary and mandibular first molars. However, no significant differences were seen between any other teeth. These results indicate that the first molar is the most sensitive tooth type at the cortical level, and provide basic data on the relationship between input from individual tooth type and brain activation. These data could be useful for understanding the neural mechanisms of individual tooth types.     

Brain regions activated during the mandibular movement tasks in functional magnetic resonance imaging

Brain regions activated during the mandibular movement were evaluated by fMRI. Eight healthy right-handed volunteers as examinees were included in this study. Echo planar imaging of fMRI were obtained with the gradient echo sequence using 1.5 T MR scanner. All examinees were subjected to complete six tasks of mandibular movement; simple mouth opening and closing movement, protrusive movement, retrusive movement, right lateral movement, left lateral movement, and imaginary mouth opening and closing movement. The stimulation paradigm consisted of 7 cycles of scans. Each cycle consisted of 10 repeated imagings during "on" and "off" periods of each 5 seconds. The head of examinee in the supine position was fixed, to minimize involuntary motions during all functional measurements, before motions of the head were measured. The following conclusions were obtained. 1. The examinations were achieved with minimal artifacts caused by motions of the head. 2. The region of motor cortex activation by the mandibular movements approximately agreed with those reported by electrophysiological methods in animals, such as cats and monkeys. 3. Activated area of motor cortex and the supplementary motor area were further extended according to the move complex mandibular movements. 4. Possible involvement of the parietal association area was indicated in the lateral movements. 5. Activation of the motor speech area was observed during lateral mandibular movement. Possibility of the involvement of the Broca's area was indicated in mandibular movement. It was thus concluded that fMRI may be useful to analyze the brain regions activated by mandibular movement.     

Face sensorimotor cortex and its neuroplasticity related to orofacial sensorimotor functions

This review describes evidence in subprimates and primates that the face primary somatosensory cortex (face SI) and primary motor cortex (face MI) are involved in sensorimotor integration and control of orofacial motor functions that include semiautomatic movements (e.g., chewing, swallowing) and voluntary movements (e.g., jaw-opening). The review also notes that the neuroplastic capabilities of the face SI and face MI have recently been documented, and may reflect or allow for functional adaptation (or maladaptation) of the orofacial sensorimotor system to an altered oral state or oral motor behaviour. They may contribute to the processes whereby patients undergoing oral rehabilitation can (or cannot) restore the lost orofacial sensorimotor functions. Such understanding is important since pain, injuries to the oral tissues, and alterations to the dental occlusion induced by tooth loss or attrition are common occurrences in humans that may sometimes be accompanied by impaired oral sensorimotor functions. Furthermore, impaired oral sensorimotor functions are common in many neurological disorders, sometimes making the most vital functions of eating, swallowing and speaking difficult and thereby reducing the patient's quality of life. It has also been well documented that such negative consequences can be improved following oral rehabilitation as patients adapt, for example, to a new dental prosthesis aimed at restoring function. Therefore, understanding the mechanisms and cortical neuroplastic processes underlying orofacial sensorimotor functions and adaptation is also important for the development of new therapeutic strategies to facilitate recovery of patients suffering from orofacial pain and sensorimotor disorders and improve their quality of life.     

口腔唇、舌、牙齿在大脑躯体感觉皮层的定位

在大脑躯体感觉皮层拓扑图中,尚没有唇、舌、牙齿的精确功能定位。本文综述近年脑功能成像技术研究人类大脑躯体感觉皮层口腔功能定位图的研究进展。     

触觉刺激三叉神经上颌支面部支配区的功能性MRI研究

目的:观察触觉刺激三叉神经上颌支(简称V2)面部支配区引起的大脑中枢反应区。方法 :选取8名健康志愿者,用棉签刺激右侧面部三叉神经上颌支的支配区,采用触觉刺激减静息的组块设计方法,采集全脑血氧水平依赖对比的功能性MRI扫描数据。结果:脑激活区为左侧初级躯体感觉皮质(BA3)、岛叶/SII、BA22、BA45,右侧BA40、BA9、BA38、BA41。结论:对侧初级躯体感觉皮质、岛叶/SII和颞上回,同侧中央后回、颞下回和颞横回及双侧前额皮质是面部V2区触觉刺激激活的脑部功能区。     

口腔内冷刺激的脑功能成像

目的：观察正常人口腔内冷水刺激时的大脑皮层反应,为其它口腔感觉的脑功能研究提供基础。方法：将16名口腔健康右利手志愿者分为两组各8名,采用软管注射装置分别进行口腔内左侧（G-L）及右侧（G-R）上颌前磨牙去离子冷水刺激,采用冷水刺激减静息的block组块设计方法,采集全脑血氧水平依赖对比的功能性磁共振成像扫描数据,并用SPM2软件包进行结果的数据分析获得口内冷刺激与静息状态对比的脑功能图像。结果：初级感觉运动区、前运动皮质、顶下小叶、楔前叶、岛叶、基底神经核有信号增强。结论：1.口内非味觉液体的温度刺激除引起口腔内体感及运动代表区的兴奋外,还引起其它相关脑区的激活;2．口内冷水感觉信息到达双侧大脑,感觉运动区为对侧激活。顶下小叶激活以同侧为主。     

Mechanisms of orofacial sensory processing in the rat insular cortex

Background

Orofacial structures involve multifarious organs, including the lips, tongue, soft and hard palates, teeth, periodontal ligaments, salivary glands, and facial skin. These organs process multiple types of sensory information that contributes to performance of the finely regulated orofacial movements. Among the types of sensory information, gustation is processed in the insular cortex, and, thus, part of the insular cortex is called the gustatory cortex. Moreover, the insular cortex receives not only gustatory information but also information on other somatosensory and chemical sensations, including nociception, thermoreception, audition, and olfaction.

Comparison of cerebral activity during teeth clenching and fist clenching: a functional magnetic resonance imaging study

Using functional magnetic resonance imaging (fMRI), we compared the cerebral activity during bilateral light fist-clenching and light-teeth clenching to provide more information on the central processing mechanisms underlying awake bruxism. Fourteen subjects participated in our study. Statistical comparisons were used to identify brain regions with significant activation in the subtraction of light fist clenching and light teeth clenching activity minus baseline. Participants also evaluated the perceived effort of clenching for each task, using a visual analogue scale of 0-100, after fMRI was performed. Bilateral light fist-clenching significantly activated the bilateral sensorimotor cortex, while light teeth-clenching was significantly associated with activation of the bilateral sensorimotor cortex, supplementary motor area, dorsolateral prefrontal cortex, and posterior parietal cortex. The VAS scores for fist clenching and teeth clenching were not significantly different. As light teeth-clenching activates a more extensive cortical network compared with light fist-clenching, we suggest that the teeth clenching may induce a more complex cerebral activity compared with the performance of a hand motor task. The clinical significance of these findings remains unknown but could perhaps be related to the propensity to trigger awake bruxism.     

种植体支持义齿患者骨感知的大脑皮层适应性初步研究

目的 采用功能性核磁共振成像(functional MRI,fMBl)对"骨感知"的中枢神经基础进行初步探讨.方法 研究对象为北京大学口腔医学院·口腔医院种植中心2005-2007年无牙颌种植修复复查患者和无牙颌初诊患者20例,共分为3组进行紧咬状态的fMRI扫描,SPM 99软件包统计分析及结果判定.结果 常规全口义齿修复(A组=8例)患者在前额叶皮层激活显著,而与咀嚼运动相关的初级感觉运动皮层激活人数较少;种植体支持固定义齿(B组=3例)患者在紧咬时皮层激活与天然牙列者更为接近,在Broca'S区、初级感觉运动皮层、前运动皮层、岛叶、颞上回、丘脑、基底神经节、海马等激活较显著;种植体支持覆盖义齿(C组=9例)患者前额叶皮层、前运动皮层、顶上回、基底神经节、丘脑等激活较多见.结论 种植体支持固定义齿患者的中枢神经系统对种植体的感觉及运动反馈更加接近于天然牙列,提示种植体支持固定义齿的修复方式能够以更自然的方式恢复患者的咀嚼功能;而常规全口义齿修复患者在咀嚼功能的恢复方面与个体运用义齿的学习、记忆及适应性有更显著的关系,有更强的个体差异性.     

面部初级感觉和运动皮层在口腔环境改变时的神经可塑性研究进展

大脑中与感觉、运动、学习、语言和认知有关的系统都集中于大脑皮层,面部初级感觉和运动皮层在控制颌面运动功能时发挥重要作用。口腔环境改变时,可以引发初级感觉和运动皮层结构改变及功能重组,初级感觉和运动皮层的神经可塑性反应了神经系统对新环境的适应能力。大脑皮层中初级感觉和运动皮层的神经可塑性研究对于揭示大脑活动规律、实施临床矫治和干预均具有重要意义。     

单侧咀嚼肌痉挛患者在不同条件下咀嚼运动的功能性磁共振成像研究

目的应用功能性磁共振成像（fMRI）技术，探讨单侧咀嚼肌痉挛（HMS）患者紧咬运动及戴软[牙合]垫紧咬运动诱发痉挛发作时，脑功能活动区域定位，试图探讨HMS发病的中枢机制及软[牙合]垫的治疗作用机制。方法4例HMS患者（2例右侧HMS，2例左侧HMS），fMRI成像采用Elscint／GE2．0T磁共振系统，时段设计，运动任务为紧咬运动及戴软[牙合]垫紧咬运动诱发痉挛发作，应用SPM99软件进行数据后处理。结果紧咬运动诱发痉挛发作时，3例表现出运动皮层的左侧优势，另1例为运动皮层双侧激活，4例均有扣带回的激活。戴软[牙合]垫紧咬运动诱发痉挛发作时，运动皮层的激活无左侧优势，3例未见扣带回的激活。结论HMS患者在戴软[牙合]垫前后紧咬运动诱发痉挛发作时，运动皮层激活的变化可能是软[牙合]垫的治疗作用机制，扣带回激活的变化可能与软[牙合]垫缓解咀嚼肌痛有关。