Kern Mark K, Arndorfer Ronald C, Hyde James S, Shaker Reza
Medical College of Wisconsin Digestive DIsease Center, Division of Gastroenterology and Hepatology, Milwaukee, WI 53226, USA.
Am J Physiol Gastrointest Liver Physiol. 2004 Feb;286(2):G304-11. doi: 10.1152/ajpgi.00201.2003. Epub 2003 Sep 25.
The external anal sphincter (EAS) plays a critical role in maintaining fecal continence; however, cerebral cortical control of voluntary EAS contraction is not completely understood. Our aims were to determine the cortical areas associated with voluntary EAS contraction and to determine the effect of two levels of sphincter contraction effort on brain activity. Seventeen asymptomatic adults (ages 21-48, 9 male) were studied using functional magnetic resonance imaging (fMRI) to detect brain activity. Studies were done in two stages. In stage 1 (10 subjects, 5 male), anal sphincter pressure was monitored from a catheter-affixed bag. Subjects performed maximal and submaximal EAS contractions during two fMRI scanning sessions consisting of alternating 10-s intervals of sustained contraction and rest. In stage 2 studies, seven subjects (4 male) performed only maximum effort sphincter contractions without a catheter. EAS contraction was associated with multifocal fMRI activity in sensory/motor, anterior cingulate, prefrontal, parietal, occipital, and insular regions. Total cortical activity volume was significantly larger (P < 0.05) for maximal (5,175 +/- 720 microl) compared with submaximal effort contractions (2,558 +/- 306 microl). Similarly, percent fMRI signal change was significantly higher (P < 0.05) for maximal (4.8 +/- 0.1%) compared with submaximal effort contractions (2.2 +/- 0.1%). Cortical region-of-interest analysis showed the incidence of insular activation to be more common in women compared with men. Other cortical regions showed no such gender differences. fMRI activity detected in stage 2 showed similar regions of cortical activation to those of the stage 1 study. Willful contraction of the EAS is associated with multifocal cerebral cortical activity. The volume and intensity of cerebral cortical activation is commensurate with the level of contractile effort.
肛门外括约肌（EAS）在维持大便失禁方面起着关键作用；然而，大脑皮层对EAS自主收缩的控制尚未完全明确。我们的目的是确定与EAS自主收缩相关的皮层区域，并确定两种程度的括约肌收缩力对大脑活动的影响。使用功能磁共振成像（fMRI）对17名无症状成年人（年龄21 - 48岁，9名男性）进行研究以检测大脑活动。研究分两个阶段进行。在第一阶段（10名受试者，5名男性），通过固定在导管上的袋子监测肛门括约肌压力。受试者在两个fMRI扫描过程中进行最大和次最大EAS收缩，每个扫描过程由持续收缩和休息交替的10秒间隔组成。在第二阶段研究中，7名受试者（4名男性）在没有导管的情况下仅进行最大用力的括约肌收缩。EAS收缩与感觉/运动、前扣带回、前额叶、顶叶、枕叶和岛叶区域的多灶性fMRI活动相关。与次最大用力收缩（2558±306微升）相比，最大用力收缩（5175±720微升）时总的皮层活动体积显著更大（P < 0.05）。同样，与次最大用力收缩（2.2±0.1%）相比，最大用力收缩（4.8±0.1%）时fMRI信号变化百分比显著更高（P < 0.05）。皮层感兴趣区域分析显示，与男性相比，女性岛叶激活的发生率更高。其他皮层区域未显示出这种性别差异。在第二阶段检测到的fMRI活动显示出与第一阶段研究相似的皮层激活区域。EAS的自主收缩与多灶性大脑皮层活动相关。大脑皮层激活的体积和强度与收缩力水平相称。
