Nikouline V V, Wikström H, Linkenkaer-Hansen K, Kesäniemi M, Ilmoniemi R J, Huttunen J
BioMag Laboratory, Medical Engineering Centre, Helsinki University Central Hospital, Helsinki, Finland.
Clin Neurophysiol. 2000 Jul;111(7):1227-33. doi: 10.1016/s1388-2457(00)00291-1.
Brain responses to auditory and visual stimuli have been previously shown to depend on the level of spontaneous brain activity in the 8-13 Hz range. Our aim was to determine whether somatosensory evoked responses are influenced by ongoing rhythmic activity in the 8-13 Hz frequency range originating in the sensorimotor cortex (mu rhythm).
We used a whole-head 122 channel magnetoencephalography (MEG) system to record somatosensory evoked fields (SEFs) in response to median nerve stimulation in 11 subjects. Spontaneous oscillations in the 8-13 Hz band over the contralateral sensorimotor cortex were evaluated in 3 different pre-stimulus time intervals using wavelet analysis.
The N20m SEF deflection did not depend on pre-stimulus activity, while the amplitude of the P35m deflection, and to a lesser extent that of the P60m deflection, showed a small positive correlation with the amplitude of the pre-stimulus mu rhythm. Although the amplitude of the mu rhythm varied by a factor of 2.3-5, the maximum variations in P35m and P60m amplitude were only 21 and 12%, respectively. The latencies of the peaks were not affected by the strength of the pre-stimulus mu rhythm.
It appears that the first excitatory cortical response (N20m) is independent of the oscillatory state (8-13 Hz frequency range) of the sensorimotor cortex. Later parts of the response (P35m and P60m) are also relatively stable compared with the large variations in mu rhythm.
先前的研究表明，大脑对听觉和视觉刺激的反应取决于8 - 13赫兹范围内的自发脑活动水平。我们的目的是确定体感诱发电位是否受源自感觉运动皮层的8 - 13赫兹频率范围内的持续节律性活动（μ节律）的影响。
我们使用全头122通道脑磁图（MEG）系统记录了11名受试者对正中神经刺激的体感诱发电场（SEF）。使用小波分析在3个不同的刺激前时间间隔内评估对侧感觉运动皮层上8 - 13赫兹频段的自发振荡。
N20m SEF偏转不依赖于刺激前活动，而P35m偏转的幅度以及在较小程度上P60m偏转的幅度与刺激前μ节律的幅度呈小的正相关。尽管μ节律的幅度变化了2.3 - 5倍，但P35m和P60m幅度的最大变化分别仅为21%和12%。峰值潜伏期不受刺激前μ节律强度的影响。
看来第一个兴奋性皮层反应（N20m）独立于感觉运动皮层的振荡状态（8 - 13赫兹频率范围）。与μ节律的大变化相比，反应的后期部分（P35m和P60m）也相对稳定。
