Study of activated area in the brain as sources of MEG and fMRI

本研究旨在开发具有高空间分辨率和高时间分辨率特点的脑功能成像。这项研究的目的是阐明神经活动和脑血流动力学的相关性，以及大脑内电活动的兴奋性与脑磁图和脑电的相关性。此外，对脑磁图和功能磁共振成像的结果进行了比较，并研究了时空信号的变化，并以两者的相关性为目的进行了查询。为了进行动物实验，研制了一种高空间分辨率的SQUID系统。该SQUID系统能够测量和识别分辨率为800μm的磁场分布。有可能用细胞尺度的空间分辨率来测量组织水平上的磁活动。利用这个系统，可以测量青蛙坐骨神经复合神经动作电流产生的磁场。此外，听觉…的测量在2 mm分辨率范围内获得了更多的小鼠诱发磁场。然而，由于测量点的不足和灵敏度低，很难确定脑磁图的来源。另一方面，为了阐明神经元活动与血流动力学反应之间的关系，采用脑磁图(MEG)和功能磁共振成像(FMRI)对初级体感皮质的激活进行了研究。研究电刺激的刺激强度对右拇指的影响。在fMRI实验中，当刺激强度增加到痛感时，激活的像素数和定义为核磁共振信号积分值的信号功率急剧增加，但这种趋势并不对应于神经元的活动。当受试者感受到强烈刺激的疼痛时，SI区的血流量增加持续较长时间，并广泛传播。SI区的神经元活动在100ms内引起，即使受试者经历疼痛，也没有广泛传播。我们还利用脑磁图和脑电对短时情景记忆进行了研究。SORECE估计显示，在左侧内侧下颞叶与有意编码过程有关的显着激活。较少

This research aims at development of functional imaging of the brain which has the feature of the high spatial resolution and the high temporal resolution. The aim of this study is clarifying the relevance of nerve activity and a hemodynamics of the brain, and the relevance of the excitability of the electric activity within a brain, and the MEG and EEG. Moreover, the result obtained by magnetoencephalography and fMRI was compared and investigating change of a spatial and temporal signal and both relevance also inquired as a purpose. For an animal experiment, a high spatial resolution SQUID system was developed. This SQUID system enabled to measure and discriminate the magnetic field pattern under 800 μm resolution. It is possible to measure the magnetic activity at a tissue level with cellular-scale spatial resolution. Using this SQUID system, magnetic Fields produced by the compound nerve action current of the frog's sciatic nerve could be measured. Moreover, measurement of auditory … More evoked magnetic fields of mice within the 2 mm resolution was succeeded. However, it is difficult to estimate the source of MEG, because of the insufficiency of measurement points and low sensitivity. On the other hand, to clarify the relationships between neuronal activity and the hemodynamic response, activations of the primary somatosensory cortex were studied using MEG (magnetoencepahlogram) and fMRI (functional magnetic resonance imaging). Effects of the stimulus intensity of the electrical stimulation to the right thumb were investigated. When the stimulus intensity increased to the pain feeling in the fMRI experiments, a number of activated pixels and signal power which was defined as the integration value of NMR signal were increase steeply, however, this inclination did not correspond to neuronal activity. An increase of blood flow at the SI area continued for a longer duration and spread widely when the subject experienced pain exposed to strong stimulation. Neuronal activity at the SI area caused within 100 ms and did not spread widely even if the subject experienced pain. We also studied the short-term episodic memory using MEG and EEG. Sourece estimation showed a significant activation in the left inferior medial temporal lobe related to intentional encoding prosesses. Less