Terao Y, Ugawa Y, Enomoto H, Furubayashi T, Shiio Y, Machii K, Hanajima R, Nishikawa M, Iwata N K, Saito Y, Kanazawa I
Department of Neurology, Division of Neuroscience, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
J Neurosci. 2001 Mar 1;21(5):1600-9. doi: 10.1523/JNEUROSCI.21-05-01600.2001.
To investigate the cortical information processing during the preparation of vocalization, we performed transcranial magnetic stimulation (TMS) over the cortex while the subjects prepared to produce voice in response to a visual cue. The control reaction time (RT) of vocalization without TMS was 250-350 msec. TMS prolonged RT when it was delivered up to 150-200 msec before the expected onset of voice (EOV). The largest delay of RT was induced bilaterally over points 6 cm to the left and right of the vertex (the left and right motor areas), resulting in 10-20% prolongation of RT. During the early phase of prevocalization period (50-100 msec before EOV), the delay induced over the left motor area was slightly larger than that induced over the right motor area, whereas, during the late phase (0-50 msec before EOV), it was significantly larger over the right motor area. Bilateral and simultaneous TMS of the left and right motor areas induced delays not significantly different from that induced by unilateral TMS during the early phase, but induced a large delay well in excess of the latter during the late phase. Thus, during the cortical preparation for human vocalization, alternation of hemispheric lateralization takes place between the bilateral motor cortices near the facial motor representations, with mild left hemispheric predominance at the early phase switching over to robust right hemispheric predominance during the late phase. Our results also suggested involvement of the motor representation of respiratory muscles and also of supplementary motor cortex.
为了研究发声准备过程中的皮质信息处理，我们在受试者准备根据视觉提示发出声音时，对其皮质进行经颅磁刺激（TMS）。无TMS时发声的对照反应时间（RT）为250 - 350毫秒。当在预期发声开始（EOV）前150 - 200毫秒施加TMS时，RT延长。RT的最大延迟是在头顶左右6厘米处的点（左右运动区）双侧诱发的，导致RT延长10 - 20%。在发声前期的早期阶段（EOV前50 - 100毫秒），左侧运动区诱发的延迟略大于右侧运动区，而在后期阶段（EOV前0 - 50毫秒），右侧运动区的延迟明显更大。双侧同时对左右运动区进行TMS在早期诱发的延迟与单侧TMS诱发的延迟无显著差异，但在后期诱发的延迟远大于后者。因此，在人类发声的皮质准备过程中，面部运动代表区附近的双侧运动皮质之间发生半球侧化交替，早期轻度左侧半球优势在后期转变为强烈的右侧半球优势。我们的结果还表明呼吸肌的运动代表区以及辅助运动皮质也参与其中。
