Source current density mapping of middle latency response and slow vertex response using a source derivation technique

采用源极求导技术，从人头皮上的中潜伏期反应（MLR）和顶慢反应（SVR）的电位波形中获得源极电流密度（SCD）波形。SCD波形在峰潜伏期和极性上与电位波形不同。MLR中Pa成分的SCD图在空间上可能由多个发生器组成：颞区的双侧偶极子和刺激对侧额区的小偶极子。如前所述，SVR中Ni和P2的SCD图表明颞区存在双侧发生器。但由于N1和P2的SCD图在空间和时间模式上存在差异，因此两者并不完全相同。从电位中减去SCD波形，得到低空间频率分量（LSFC）。与头皮上的电位波形相比，SCD波形中的N1和P2的潜伏期均减小。相反，LSFC波形中的潜伏期延长。SCD图中N1的源区域最初出现在颞区附近，刺激耳的对侧，随着时间的推移，出现在两个颞区的限制源区域。P2在SCD和LSFC中的图显示位于两个颞区的汇区和位于顶点附近的源区。这种P2汇-源模式不随时间变化，由此推断，N1可能是由双侧颞区产生的，其中包括运动的深偶极子的贡献。P2被认为起源于双侧颞叶部位的解剖学固定位置。

Source current density (SCD) waveforms were obtained from potential waveforms of the middle latency response (MLR) and slow vertex response (SVR) over the human scalp using a source derivation technique. The SCD waveforms were different from the potential waveforms in the peak latency and polarity. The SCD map of the Pa component in MLR might be composed of more than one generator spatially : the bilateral dipoles in the temporal region and small dipole in the frontal region contralateral to stimulation. The SCD maps of Ni and P2 in SVR suggested bilateral generators in the temporal region as previously reported. However, the two were not identical because of there being a difference in the spatial and temporal patterns between the SCD maps of N1 and P2.By subtracting the SCD waveform from the potential, the low spatial frequency component(LSFC) was obtained. The latencies of both N1 and P2 in the SCD waveform were decreased in comparison to the potential waveform on the scalp. In contrast, the latencies in the LSFC waveform were prolonged. The source region of N1 in the SCD maps appeared initially in the vicinity of the temporal region, contralateral to the stimulated ear, and with time, appeared as restricted source regions in both temporal regions. The maps of P2 in the SCD and LSFC showed a sink region located in both temporal areas, and source regions in the vicinity of the vertex. This P2 sink-source pattern did not change with time.It was concluded that the N1 might be generated from the bilateral temporal regions including contributions from moving deep dipoles. The P2 was thought to originate from an anatomically fixed location in the bilateral temporal sites.