线圈与颅骨距离对经颅磁刺激运动诱发电位的影响。
The influence of coil-skull distance on transcranial magnetic stimulation motor-evoked responses.
作者信息
Cukic M, Kalauzi A, Ilic T, Miskovic M, Ljubisavljevic M
机构信息
Department of Neurophysiology, Institute for Medical Research, Belgrade, PO Box 11121, Serbia.
出版信息
Exp Brain Res. 2009 Jan;192(1):53-60. doi: 10.1007/s00221-008-1552-0. Epub 2008 Sep 12.
We have investigated the effects of changing the coil-to-skull distance on the motor-evoked responses (MEP) induced with two different magnetic stimulator coils (80 mm round and figure-of-eight coil) at rest and during voluntary muscle contraction. The changes in MEP latency, amplitude and silent period (SP) duration induced by stimulation directly upon the skull, and 1 cm away from the skull were analyzed by computing the probability density distribution (PDD) for the responses obtained from all subjects. This measure corresponds to the finite probability that the event occurs within a given area. Overall, the results were consistent with a distance-induced decrease in magnetic field strength. However, the increase in coil-to-skull distance induced a higher probability of longer latencies in active muscle when stimulating with either coil. Also, stimulating at a distance with the figure-of-eight coil increased the probability of a longer SP duration. The stimulation strength at the two distances was comparable because it was set based on the motor threshold obtained for each distance. Therefore, our results are not entirely compatible with the established exponential drop in magnetic field with increasing distance. Rather, they suggest that a more complex set of interactions occurs in the cortex. The results imply that distinct patterns of cortical network activation may exist related to the distance-induced alterations when the coil is moved away from the skull. Further studies are required to elucidate the precise nature of the distance-related interactions of the magnetic field with the cortex.
我们研究了改变线圈与颅骨距离对在静息和自主肌肉收缩状态下,使用两种不同磁刺激线圈(80毫米圆形和8字形线圈)诱发的运动诱发电位(MEP)的影响。通过计算所有受试者获得的反应的概率密度分布(PDD),分析了直接在颅骨上以及距颅骨1厘米处进行刺激所诱发的MEP潜伏期、波幅和静息期(SP)持续时间的变化。该测量对应于事件在给定区域内发生的有限概率。总体而言,结果与距离导致磁场强度降低一致。然而,无论使用哪种线圈进行刺激,线圈与颅骨距离的增加都会导致主动肌肉中潜伏期延长的概率更高。此外,使用8字形线圈在一定距离处进行刺激会增加SP持续时间延长的概率。两个距离处的刺激强度相当,因为它是根据每个距离获得的运动阈值设置的。因此,我们的结果并不完全符合随着距离增加磁场强度呈指数下降的既定规律。相反,它们表明在皮质中发生了一组更复杂的相互作用。结果意味着当线圈远离颅骨时,可能存在与距离诱导的改变相关的不同皮质网络激活模式。需要进一步研究以阐明磁场与皮质的距离相关相互作用的确切性质。