Schluter N D, Rushworth M F, Passingham R E, Mills K R
Department of Experimental Psychology, University of Oxford, UK.
Brain. 1998 May;121 ( Pt 5):785-99. doi: 10.1093/brain/121.5.785.
It is known that damage to the left hemisphere can lead to movement deficits, and that patients with apraxia have difficulty in selecting movements. Neurophysiological recording studies and lesion studies have shown that the premotor cortex is important for the selection of movements in monkeys. In this study we used transcranial magnetic stimulation (TMS) to disrupt the processing in human premotor cortex. We applied TMS to normal healthy volunteers over the premotor and primary motor areas while they carried out choice reaction time and simple reaction-time tasks. We measured response times of either hand as subjects were stimulated over the left and right hemisphere separately. We found that we were able to delay responses by stimulating at short cue-stimulus intervals (100-140 ms) over premotor cortex and at longer cue-stimulus intervals (300-340 ms) over primary motor cortex while subjects performed the choice reaction-time task with the contralateral hand. We were also able to delay responses with the ipsilateral hand while stimulating over the left premotor cortex, but not while stimulating over the right premotor cortex or either sensorimotor cortex. Premotor cortex stimulation alone disrupts an early stage of movement selection; motor cortex stimulation disrupts the movements at a later stage of execution. There was no distinguishing short cue-stimulus interval effect when premotor cortex was stimulated in the simple reaction time paradigm, where the movement selection demands of the task are kept to a minimum. We conclude that the premotor cortex is important for selecting movements after a visual cue and that the left hemisphere is dominant for the rapid selection of action.
众所周知，左半球受损会导致运动功能障碍，失用症患者在选择动作时存在困难。神经生理学记录研究和病灶研究表明，运动前区皮质对猴子的动作选择很重要。在本研究中，我们使用经颅磁刺激（TMS）来干扰人类运动前区皮质的加工过程。我们在正常健康志愿者执行选择反应时间和简单反应时间任务时，对其运动前区和初级运动区施加TMS。当分别在受试者的左半球和右半球进行刺激时，我们测量了受试者任一只手的反应时间。我们发现，当受试者用对侧手执行选择反应时间任务时，通过在运动前区皮质以短线索-刺激间隔（100 - 140毫秒）进行刺激以及在初级运动区皮质以长线索-刺激间隔（300 - 340毫秒）进行刺激，我们能够延迟反应。当在左运动前区皮质进行刺激时，我们也能够延迟同侧手的反应，但在右运动前区皮质或任一感觉运动区皮质进行刺激时则不能。单独的运动前区皮质刺激会干扰动作选择的早期阶段；运动皮质刺激会在执行的后期阶段干扰动作。在简单反应时间范式中，当刺激运动前区皮质时，没有明显的短线索-刺激间隔效应，在该范式中任务的动作选择要求被保持在最低限度。我们得出结论，运动前区皮质对于视觉线索后的动作选择很重要，并且左半球在快速动作选择方面占主导地位。
