Nikolova M, Pondev N, Christova L, Wolf W, Kossev A R
Institute of Biophysics, Bulgarian Academy of Sciences, Acad G Bontchev Str, Bldg 21, Sofia, Bulgaria.
Eur J Appl Physiol. 2006 Sep;98(2):212-9. doi: 10.1007/s00421-006-0265-y. Epub 2006 Aug 25.
The effect of transcranial magnetic stimulation (TMS) on reaction time (RT) and motor cortex excitability in the premovement period was investigated. Single and paired-pulse TMS with 3 and 13 ms interstimulus intervals (ISI) were applied to the left motor cortex at different delays after a visual command for isometric right hand index finger abduction. Motor evoked potentials (MEPs) recorded from the right first dorsal interosseous (FDI) were analysed to assess cortex excitability. The MEPs in response to single pulse TMS were gradually increased in the premovement period in general, but strongly augmented in a period of 90-100 ms before the voluntary myoelectrical activity (EMG) onset. In paired-pulse TMS (13 ms ISI), the MEP augmentation was smaller but started earlier before the EMG burst, and a gradual increase of MEP amplitudes was not evident. In case of 3 ms ISI, the expected intracortical inhibition (ICI) was evident only when TMS preceded the voluntary EMG by an interval of more than 60 ms, but at shorter intervals, rather some MEP augmentation was observed. Generally, the augmentation of MEPs in the premovement period was more pronounced in single pulse TMS. Most strikingly, a dead band period without MEP occurrences was observed within an interval of 30-50 ms before the voluntary EMG. In conclusion, parallel action of intracortical facilitation (ICF) and ICI as well as different dynamic behaviour of ICF and pre movement facilitation may explain the earlier mentioned effects. Moreover, this leads to an extended description of the rather subtle TMS influence on RT.
研究了经颅磁刺激（TMS）对运动前期间反应时间（RT）和运动皮层兴奋性的影响。在视觉指令下达后，以不同延迟时间对左侧运动皮层施加间隔时间分别为3毫秒和13毫秒的单脉冲和双脉冲TMS，指令为右手食指等长外展。分析从右侧第一背侧骨间肌（FDI）记录的运动诱发电位（MEP）以评估皮层兴奋性。一般来说，对单脉冲TMS的反应中，MEP在运动前期间逐渐增加，但在自主肌电活动（EMG）开始前90 - 100毫秒期间显著增强。在双脉冲TMS（13毫秒间隔时间）中，MEP增强较小，但在EMG爆发前开始得更早，且MEP幅度没有明显的逐渐增加。在间隔时间为3毫秒时，仅当TMS在自主EMG之前的间隔超过60毫秒时，预期的皮层内抑制（ICI）才明显，但在较短间隔时，反而观察到一些MEP增强。一般来说，单脉冲TMS在运动前期间MEP的增强更为明显。最显著的是，在自主EMG前30 - 50毫秒的间隔内观察到一个没有MEP出现的静息期。总之，皮层内易化（ICF）和ICI的并行作用以及ICF和运动前易化的不同动态行为可能解释了上述效应。此外，这导致对TMS对RT的相当微妙的影响有了更详细的描述。
