Wikström H, Roine R O, Salonen O, Aronen H J, Virtanen J, Ilmoniemi R J, Huttunen J
BioMag Laboratory, Helsinki University Central Hospital, Finland.
Electroencephalogr Clin Neurophysiol. 1997 Nov;104(6):480-7. doi: 10.1016/s0168-5597(97)00055-5.
The objective of the present study was to evaluate the normal interhemispheric variability of the locations and activation strengths of the somatosensory cortices. Somatosensory evoked magnetic fields (SEFs) were recorded with a 122-channel magnetometer in 23 healthy subjects (mean age 57 years) to stimulation of left and right median nerves. Equivalent current dipole (ECD) strengths and locations were determined for the main SEF deflections at the contralateral primary sensorimotor (SMI) and secondary somatosensory (SIIc) cortices. In a Cartesian co-ordinate system, defined by the preauricular points and the nasion, the SMI sources were slightly but significantly more laterally and anteriorly located in the right than in the left hemisphere. No systematic co-ordinate asymmetries were found for the SIIc sources. In individual subjects, the interhemispheric differences in the ECD co-ordinates averaged less than 6 mm at both SMI and SIIc. The group means of the source strengths did not differ between the hemispheres, but individual differences were on average 20% for the SMI and 65% for the SIIc sources. We conclude that at the individual level, the median nerve SEFs from SMI can be used to detect abnormally large interhemispheric asymmetries of source locations in the centimetre scale.
本研究的目的是评估体感皮层位置和激活强度的正常半球间变异性。使用122通道磁力计记录了23名健康受试者（平均年龄57岁）在刺激左右正中神经时的体感诱发磁场（SEF）。确定了对侧初级感觉运动（SMI）和次级体感（SIIc）皮层主要SEF偏转的等效电流偶极（ECD）强度和位置。在由耳前点和鼻根定义的笛卡尔坐标系中，SMI源在右侧比左侧半球略更偏外侧和靠前，但差异显著。未发现SIIc源存在系统性的坐标不对称。在个体受试者中，SMI和SIIc处ECD坐标的半球间差异平均小于6毫米。源强度的组均值在半球间无差异，但个体差异在SMI源平均为20%，在SIIc源平均为65%。我们得出结论，在个体水平上，来自SMI的正中神经SEF可用于检测厘米尺度上源位置异常大的半球间不对称。
