Human Motor Control Section, NINDS, National Institutes of Health, Bethesda, MD 20892-1428, USA.
Clin Neurophysiol. 2010 Jan;121(1):98-103. doi: 10.1016/j.clinph.2009.09.010. Epub 2009 Nov 11.
The aim of this study was to further characterize surround inhibition (SI) in the primary motor cortex (M1) by comparing its magnitude and time course during a simple reaction time task (SRT) and a choice reaction time task (CRT).
In both the SRT and the CRT, subjects performed the same right index finger flexion in response to an acoustic signal. For CRT, the alternative choice was a similar movement using the left index finger, as distinguished by a different tone. In both tasks, single pulse transcranial magnetic stimulation (TMS) was applied at rest, 75ms (T1) and 25ms before EMG onset (T2), and during the first peak of EMG (T3) in the right first dorsal interosseous muscle (FDI). Motor evoked potentials (MEPs) were recorded from both FDIs, which act as synergists in the task, and the right surrounding, relaxed abductor pollicis brevis muscle (APB).
For right hand movement, SI started earlier and was more pronounced for CRT compared to SRT. For left hand movement in the CRT, SI was similar to that of right hand movement.
We conclude that SI occurs earlier and stronger with increasing task difficulty.
The timing as well as the bilateral effect of the inhibition suggests that motor areas involved in motor planning, proximate to the motor cortex, contribute to the genesis of surround inhibition.
本研究旨在通过比较简单反应时任务（SRT）和选择反应时任务（CRT）中 surround inhibition（SI）的幅度和时程，进一步描述初级运动皮层（M1）中的 SI。
在 SRT 和 CRT 中，受试者均以相同的右食指运动来响应声学信号。对于 CRT，替代选择是使用左食指进行类似的运动，通过不同的音调来区分。在这两个任务中，单脉冲经颅磁刺激（TMS）在静息时（T1）、肌电图（EMG）起始前 75ms（T2）和 25ms 时（T2）以及右侧第一背侧骨间肌（FDI）的 EMG 第一个峰值时（T3）施加。运动诱发电位（MEPs）分别从 FDIs 和右侧周围放松的拇指外展短肌（APB）记录，它们在任务中作为协同肌。
对于右手运动，与 SRT 相比，CRT 中的 SI 开始更早且更为明显。对于 CRT 中的左手运动，SI 与右手运动相似。
我们得出结论，随着任务难度的增加，SI 出现得更早且更强。
抑制作用的时间和双侧效应表明，参与运动规划的运动区域，靠近运动皮层，有助于 surround inhibition 的产生。
