Department of Psychiatry (NRU), Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada.
Neuroscientist. 2009 Oct;15(5):507-24. doi: 10.1177/1073858409333076. Epub 2009 Jul 21.
Together, thousands of neurons with similar function make up topographically oriented sensory cortex maps that represent contralateral body parts. Although this is an accepted model for the adult cortex, whether these same rules hold after stroke-induced damage is unclear. After stroke, sensory representations damaged by stroke remap onto nearby surviving neurons. Here, we review the process of sensory remapping after stroke at multiple levels ranging from the initial damage to synapses, to their rewiring and function in intact sensory circuits. We introduce a new approach using in vivo 2-photon calcium imaging to determine how the response properties of individual somatosensory cortex neurons are altered during remapping. One month after forelimb-area stroke, normally highly limb-selective neurons in surviving peri-infarct areas exhibit remarkable flexibility and begin to process sensory stimuli from multiple limbs as remapping proceeds. Two months after stroke, neurons within remapped regions develop a stronger response preference. Thus, remapping is initiated by surviving neurons adopting new roles in addition to their usual function. Later in recovery, these remapped forelimb-responsive neurons become more selective, but their new topographical representation may encroach on map territories of neurons that process sensory stimuli from other body parts. Neurons responding to multiple limbs may reflect a transitory phase in the progression from their involvement in one sensorimotor function to a new function that replaces processing lost due to stroke.
数千个具有相似功能的神经元组成了具有拓扑定向的感觉皮层图谱，代表着对侧身体部位。尽管这是成人皮层的公认模型，但在中风引起的损伤后，这些相同的规则是否仍然适用尚不清楚。中风后，中风损伤的感觉代表区域重新映射到附近存活的神经元上。在这里，我们在多个层面上回顾了中风后的感觉重新映射过程，从最初的突触损伤到它们的重新布线以及在完整的感觉回路中的功能。我们介绍了一种新的方法，使用体内双光子钙成像来确定单个体感皮层神经元的反应特性在重新映射过程中是如何改变的。在前肢区域中风后一个月，在存活的梗死周边区域中通常高度肢体选择性的神经元表现出显著的灵活性，并随着重新映射的进行开始处理来自多个肢体的感觉刺激。中风后两个月，重新映射区域内的神经元发展出更强的反应偏好。因此，重新映射是由存活的神经元除了它们的通常功能之外，采用新的角色来启动的。在恢复后期，这些重新映射的前肢反应神经元变得更加选择性，但它们的新拓扑表示可能会侵犯处理来自其他身体部位感觉刺激的神经元的地图区域。对多个肢体做出反应的神经元可能反映了从参与一种感觉运动功能到取代因中风而丧失的功能的新功能的进展中的一个过渡阶段。
