Yamamoto T, Williamson S J, Kaufman L, Nicholson C, Llinás R
Department of Physiology and Biophysics, New York University Medical Center, NY 10016.
Proc Natl Acad Sci U S A. 1988 Nov;85(22):8732-6. doi: 10.1073/pnas.85.22.8732.
The performance of a cryogenic system that monitors the extracranial magnetic field simultaneously at 14 positions over the scalp has been evaluated to determine the accuracy with which neuronal activity can be located within the human brain. Initially, measurements were implemented on two model systems, a lucite sphere filled with saline and a model skull. With a magnetic field strength similar to that of a human brain, the measurement and analysis procedures demonstrated a position accuracy better than 3 mm, for a current dipole 3 cm beneath the surface. Subsequently, measurements of the magnetic field pattern appearing 100 ms after the onset of an auditory tone-burst stimulus were obtained in three human subjects. The location of the current dipole representing intracellular ionic current in active neurons of the brain was determined, with 3-mm accuracy, to be within the cortex forming the floor of the Sylvian fissure of the individual subjects, corresponding closely to the Heschl gyrus as determined from magnetic resonance images. With the sensors placed at appropriate positions, the locations of neuronal sources for different tone frequencies could be obtained without moving the recording instrument. Adaptation of activity in human auditory cortex was shown to reveal long-term features with a paradigm that compared response amplitudes for three tones randomly presented.
对一个低温系统的性能进行了评估，该系统可同时在头皮上的14个位置监测颅外磁场，以确定在人脑中定位神经元活动的准确性。最初，在两个模型系统上进行了测量，一个是充满盐水的有机玻璃球体和一个模型颅骨。在与人类大脑磁场强度相似的情况下，测量和分析程序表明，对于表面以下3厘米处的电流偶极子，位置精度优于3毫米。随后，在三名人类受试者中获得了在听觉纯音猝发刺激开始后100毫秒出现的磁场模式的测量结果。代表大脑活跃神经元细胞内离子电流的电流偶极子的位置被确定，精度为3毫米，位于形成个体受试者大脑外侧裂底部的皮质内，与磁共振图像确定的颞横回密切对应。通过将传感器放置在适当位置，无需移动记录仪器就能获得不同音调频率的神经元源位置。人类听觉皮层的活动适应性通过一种范式得以展现，该范式比较了随机呈现的三个音调的反应幅度，以揭示长期特征。
