Milner Theodore E, Franklin David W, Imamizu Hiroshi, Kawato Mistuo
School of Kinesiology, Simon Fraser University, Burnaby, Canada.
Neuroimage. 2007 Jun;36(2):388-95. doi: 10.1016/j.neuroimage.2007.01.057. Epub 2007 Mar 23.
We performed whole-brain fMRI to explore the neural mechanisms that contribute to the ability to manipulate an object with complex dynamics. Subjects grasped a weighted flexible ruler and balanced it in an unstable equilibrium position as an archetype of grasping an object with complex dynamics. This was contrasted with squeezing a soft foam ball as an archetype of grasping an object with simple dynamics. We hypothesized that changes in activity in primary motor cortex (MI) would be similar under the two conditions, since muscle activation was matched, which was confirmed. We hypothesized further that the cerebellum would be selectively activated when manipulating the flexible ruler because the ability to make the adjustments necessary to balance the ruler would require an internal dynamics model, represented in the cerebellum. As predicted, the ipsilateral cerebellum was strongly activated when balancing the weighted ruler whereas only moderate activation was found when squeezing the foam ball. We also found evidence for selective activation of areas, previously implicated in tactile object recognition, when holding the flexible ruler. We speculate that these areas, which include secondary somatosensory cortex (SII), Brodmann area 40 and insula, integrate tactile and proprioceptive information in the context of controlling the orientation of the flexible ruler and provide appropriate feedback to MI. We speculate that the failure to find activation of these areas when squeezing the ball was due to the fact that tactile stimulation was entirely self-produced, resulting in the attenuation of cortical sensory activity (Blakemore, S.-J., Wolpert, D.M., Frith, C.D., 1998. Central cancellation of self-produced tickle sensation. Nat. Neurosci. 1, 635-640, Blakemore, S.-J., Frith, C.D., Wolpert, D.M., 2001. The cerebellum is involved in predicting the sensory consequences of action. NeuroReport 12, 1879-1884).
我们进行了全脑功能磁共振成像（fMRI），以探究有助于操控具有复杂动力学特性物体的神经机制。受试者握住一个加重的柔性尺子，并将其平衡在不稳定的平衡位置，以此作为操控具有复杂动力学特性物体的典型范例。这与挤压一个软泡沫球形成对比，挤压软泡沫球是操控具有简单动力学特性物体的典型范例。我们假设，在两种条件下初级运动皮层（MI）的活动变化会相似，因为肌肉激活是匹配的，这一点得到了证实。我们进一步假设，在操控柔性尺子时小脑会被选择性激活，因为平衡尺子所需的调整能力需要一个内部动力学模型，该模型由小脑表征。正如预测的那样，在平衡加重尺子时同侧小脑被强烈激活，而挤压泡沫球时仅发现适度激活。我们还发现，在握住柔性尺子时，先前与触觉物体识别相关的区域有选择性激活的证据。我们推测，这些区域包括次级体感皮层（SII）、布罗德曼40区和脑岛，在控制柔性尺子方向的背景下整合触觉和本体感觉信息，并向MI提供适当反馈。我们推测，挤压球时未发现这些区域激活是由于触觉刺激完全是自我产生的，导致皮层感觉活动减弱（布莱克莫尔，S.-J.，沃尔珀特，D.M.，弗里斯，C.D.，1998年。自我产生的瘙痒感觉的中枢抑制。《自然神经科学》1，635 - 640；布莱克莫尔，S.-J.，弗里斯，C.D.，沃尔珀特，D.M.，2001年。小脑参与预测动作的感觉后果。《神经报告》12，1879 - 1884）。
