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

触觉是根据身体表面在地形图的初级躯体感觉皮质中编码的。这种地形表示可以根据培训和经验进行修改。这种大脑的可塑性是新表达或加强的突触连接的结果。这种影响可以用脑磁图(MEG)无创地在人类身上测量，表现为皮质表面的激活增加或更大的激活区域。大脑的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，通过测量由手指代表之间的距离指示的躯体视觉手部区域的大小，来客观地监测躯体感觉皮质的可塑性重组。利用脑磁图可以定位手指在人体体感皮质中的表达。手指之间的距离可以从多个脑磁图记录中获得，刺激一个手指接着另一个手指。然而，两次录制之间的磁头移动会导致太大的误差。在我们的新程序中，我们将用不同频率的振动同时刺激多个手指。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。这些回应将被本地化。手指代表之间的距离可以高精度地测量，因为所有的记录都是同时进行的，并且同样受到头部运动的影响。我们将研究手指位置和注意效应之间的可能交互作用，以优化这一过程。总而言之，我们将开发一种高精度的方法来测量大脑皮层中身体各部分之间的距离。所获得的距离测量随时间的变化表明可塑性重组，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.