Marquart M, Birn R, Haughton V
Department of Radiology, Medical College of Wisconsin, Milwaukee, USA.
AJNR Am J Neuroradiol. 2000 Jan;21(1):94-8.
The "single-event" technique has been used as an alternative to the "block-trial" method to detect activation that may be accompanied by head motion. The purpose of this study was to compare the two methods for measuring activation in the sensorimotor cortex secondary to motor tasks.
Functional MR imaging data were acquired from six participants as they performed tasks with their fingers, tongues, and toes in a block-trial and a single-event paradigm. For the block trial, the participant was instructed to perform the task when cued at a rapid self-timed rate for 15 seconds, alternating with 15 seconds of rest. Five periods of task performance and six rest periods were included in one acquisition. For the single-event method, the participant performed the task a single time every 15 seconds when cued by the investigator, for a total of 21 times. Using conventional parcellation methods, activation was detected by a cross-correlation technique and was classified as occurring in the sensorimotor cortex, supplementary motor area (SMA), or as nonspecific. Differences between the two acquisition paradigms were tested using the standard t test at a significance level of P < .05.
Activation was identified by both the block-trial and the single-event methods for the finger task, for the tongue task, and inconsistently for the toe task. More motion artifact occurred in conjunction with the toe and tongue tasks than with the finger tasks. On average, more activated pixels were identified by the single-event method than by the block-trial method. For these motor tasks, however, a larger percentage of pixels detected by the block-trial method than by the single-event method were specific for the sensorimotor cortex or SMA as sites of activation.
For the tongue and the toe movement tasks, which may produce some head motion artifacts, the single-event paradigm provides a useful alternative to the block-trial method for identifying the sensorimotor cortex or SMA. It does not achieve a greater percentage of activation within primary motor areas. For the finger movement task, which does not usually produce head motion artifacts, the block-trial method generally produced a greater percentage of activated pixels in the sensorimotor cortex or SMA than did the single-event method.
“单事件”技术已被用作“组块试验”方法的替代方法，以检测可能伴随头部运动的激活情况。本研究的目的是比较这两种测量运动任务继发的感觉运动皮层激活的方法。
从6名参与者在组块试验和单事件范式下用手指、舌头和脚趾执行任务时采集功能磁共振成像数据。对于组块试验，参与者被指示在快速自我计时的提示下以15秒的时间执行任务，与15秒的休息时间交替进行。一次采集包括5个任务执行期和6个休息期。对于单事件方法，参与者在研究者提示下每15秒执行一次任务，共执行21次。使用传统的脑区划分方法，通过互相关技术检测激活情况，并将其分类为发生在感觉运动皮层、辅助运动区（SMA）或非特异性激活。使用标准t检验在P <.05的显著性水平下测试两种采集范式之间的差异。
组块试验和单事件方法均识别出手指任务、舌头任务的激活，而脚趾任务的激活情况不一致。与手指任务相比，脚趾和舌头任务伴随更多的运动伪影。平均而言，单事件方法识别出的激活像素比组块试验方法更多。然而，对于这些运动任务，组块试验方法检测到的像素中，作为激活部位的感觉运动皮层或SMA特异性像素的百分比高于单事件方法。
对于可能产生一些头部运动伪影的舌头和脚趾运动任务，单事件范式为识别感觉运动皮层或SMA提供了一种有用的替代组块试验方法。它在初级运动区内并未实现更高的激活百分比。对于通常不会产生头部运动伪影的手指运动任务，组块试验方法在感觉运动皮层或SMA中产生的激活像素百分比通常比单事件方法更高。
