Tiihonen J, Hari R, Hämäläinen M
Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland.
Electroencephalogr Clin Neurophysiol. 1989 Jul-Aug;74(4):290-6. doi: 10.1016/0168-5597(89)90059-2.
We have recorded early components of somatosensory evoked magnetic fields with a sensitive 7-channel first-order gradiometer using a wide recording passband (0.05-2000 Hz) and high sampling frequency (8000 Hz). The left median nerve was stimulated at the wrist and responses were recorded over the right hemisphere. The responses typically consisted of a N20m peaking at 18-20 msec, a small P22m peaking at 21-23 msec and a P27m peaking at 29-31 msec. The topography of N20m could be explained by a tangential current dipole in the posterior wall of the central sulcus (probably in area 3b). The equivalent dipoles of P27m were located on average 10 mm antero-medially to the sources of N20m. This suggests that P27m may get a contribution from the anterior wall of the central sulcus. An increase of stimulus repetition rate from 2 to 5 Hz decreased the amplitude of P27m more than that of N20m, which implies that these two deflections are generated by different neural networks.
我们使用灵敏的7通道一阶梯度仪，通过宽记录通带（0.05 - 2000 Hz）和高采样频率（8000 Hz）记录了体感诱发电磁场的早期成分。在腕部刺激左侧正中神经，并在右侧半球记录反应。反应通常包括一个在18 - 20毫秒达到峰值的N20m、一个在21 - 23毫秒达到峰值的小P22m和一个在29 - 31毫秒达到峰值的P27m。N20m的地形图可以用中央沟后壁（可能在3b区）的切向电流偶极子来解释。P27m的等效偶极子平均位于N20m源前内侧10毫米处。这表明P27m可能从中央沟的前壁获得贡献。刺激重复率从2 Hz增加到5 Hz时，P27m的幅度比N20m的幅度下降得更多，这意味着这两个偏转是由不同的神经网络产生的。
