Neuromagnetic Study on Higher Brain Functions

脑磁图（MEG）是一种非侵入性技术，它测量的磁场主要来自皮质锥体神经元顶端树突的细胞内电流，这是由兴奋性突触输入引起的。在这个项目中，分析了体感诱发、视觉诱发和运动相关的磁场。(1)记录正中神经电刺激引起的大脑磁场。在对侧头皮的初级体感皮层（SI）产生了20 ms和60 ms的反应峰值。第一个成分暗示细胞内电流的存在，通过锥体神经元的顶端树突，从SI的深层流向表面层，这似乎是由丘脑对SI的深层输入引起的。第二个成分似乎是通过皮层内神经元回路在SI的浅层代表突触活动。(2)视觉刺激在视野中心周围的4或8个位置呈现。视刺激在视野中的位置不同，反应的波形和分布也有很大的不同。据估计，负责第一个分量（峰值潜伏期，75毫秒）的电流偶极子位于枕叶中线附近，可能是纹状皮层。(3)研究了与视觉启动的手指运动相关的大脑磁场。在运动开始前，在操作手指的对侧头皮上记录磁场变化。该分量的估计电流偶极子指向中央沟周围的前方。这意味着存在从中央沟前岸浅层到深层的树突内电流。先前的动物实验提供了对这一成分的解释，即通过小脑-丘脑-皮层通路激活运动皮层的手部区域。这些结果表明，神经磁记录为研究人类大脑的感觉、运动和综合功能提供了一种有效的非侵入性方法，特别是当与适当的动物实验相结合时。少

A non-invasive technique, magnetoencephalography(MEG)measures the magnetic fields originating mainly from the intracellular current flow through the apical dendrites of cortical pyramidal neurons, which is caused by excitatory synaptic inputs. In this project, somatosensory-evoked, visually-evoked and movement-related magnetic fields were analyzed.(1)Cerebral magnetic fields elicited by the electrical stimulation of the median nerve were recorded. Responses at a peak latecy of 20 ms and 60 ms were generated in the primary somatosensory cortex(SI)over the contralateral scalp. The first component implies the existence of the intracellular current flow through the apical dendrites of pyramidal neurons directed from the deep layr to the superficial layr of SI, which seems to be caused by thalamic inputs to the deep layrs of SI.The second component seems to represent the synaptic activity at the superficial layr of SI probably through the intracortical neuronal circuits.(2)Visual stimuli we … More re presented at 4 or 8 positions around the center of the visual field. Waveform and distribution of the responses greatly varied depending on the stimulus position within the visual field. The electrical current dipole responsible for the first component(peak latency, 75 ms)was estimated to be around the midline of the occipital lobe, presumably the striate cortex.(3)Cerebral magnetic fields associated with visually initiated finger movements were studied. Magnetic field change preceding the onset of the movements was recorded over the contralateral scalp of the operating finger. The estimated current dipole of this component was directed anteriorly around the central sulcus. This implies the existence of the intradendritic current flow directed from the superficial layr to the deep layr of the anterior bank of the central sulcus. Previous animal experiments provide the interpretation of this component to be the activation of the hand area of the motor cortex through the cerebello-thalamo-cortical pathway.These results indicate that neuromagnetic recordings provide an effective non-invasive approach to the studies of the sensory, motor and integrative functions of the human brain, especially when combined with appropriate animal experiments. Less