Improved characterization of human somatosensory cortex using simultaneous vibro-tactile stimulation of multiple digits

触觉在初级躯体感觉皮层中编码，形成相应于体表的地形图。这种地形表示可以根据训练和经验进行修改。这种大脑可塑性来自于新表达或加强的突触连接。这种效应可以在人类中使用脑磁图（MEG）作为皮层表面上增加的激活或更大的激活区域来非侵入性地测量。大脑可塑性是中风成功康复的重要因素。我们将开发一种新的方法，通过测量手指代表之间的距离所指示的躯体位置的手面积的大小来客观地监测躯体感觉皮层的塑性重组。脑磁图可以定位人类躯体感觉皮层的手指表征。手指之间的距离可以从多个MEG记录中获得，其中一个手指接一个手指地刺激。然而，记录之间的头部移动会导致太大的误差。通过我们的新程序，我们将同时刺激多个手指，并以不同的频率振动。我们将记录振动刺激频率下的大脑活动，并可以将每个手指的反应分开。这些反应将是局部的。手指代表之间的距离可以以高精度测量，因为所有记录都是同时进行的，并且同样受到头部运动的影响。我们将调查手指定位和注意力的影响之间可能的相互作用，以优化程序。总之，我们将开发一种高度精确的方法来测量大脑皮层中身体部位表征之间的距离。所获得的距离测量值随时间的变化指示塑性重组，例如作为治疗干预的效果。

Tactile sensation is encoded in the primary somatosensory cortex in topographical maps accordingly to the body surface. This topographical representation can be modified as the result of training and experience. This brain plasticity results from newly expressed or strengthened synaptic connections. The effect can be measured in humans noninvasively using magnetoencephalography (MEG) as increased activation or larger activated area on the cortical surface. Brain plasticity is an important factor for successful recovery from a stroke. We shall develop a new method for objectively monitoring of plastic reorganization in somatosensory cortex by measuring the size of the somatotopic hand area as indicated by the distance between finger representation. The finger representation in human somatosensory cortex can be localized with the MEG. The distance between fingers can be obtained from multiple MEG recordings with stimulating one finger after the other. However, head movements between recordings cause too large errors. With our new procedure we will stimulate multiple fingers at the same time with vibrations of different rate. We shall record brain activity at the frequencies of the vibration stimuli and can separate the responses from each finger. Those responses will be localized. The distance between finger representation can be measured with high precision because all recordings were done at the same time and were affected by head movements equally. We shall investigate the possible interactions between finger localizations and effects of attention in order to optimize the procedure. In summary we shall develop a highly precise method for measuring distances between body part representations in the cortex. Changes over time in the obtained distance measure indicate plastic reorganisation e.g. as the effect of therapeutic intervention.