Despite state-of-the-art surgical and postoperative treatment, median nerve transection causes lasting impaired hand function due to limitations in the nerve’s reinnervation ability. The defective innervation and thus controllability of the affected hand can shape the brain’s control of manual behaviors. Earlier studies of changes in the processing of tactile stimuli have focused mainly on stimulation of the reinnervated hand and lack sufficient control over the brain’s use of the tactile input in perceptual terms. Here we used fMRI to measure brain activity (BOLD-signal) in 11 people with median nerve injury and healthy controls (N = 11) when performing demanding tactile tasks using the tip of either the index or little finger of either hand. For the nerve-injured group, the left median nerve had been traumatically transected in the distal forearm and surgically repaired on average 8 years before the study. The hand representation of their contralesional (right) primary somatosensory cortex (S1) showed greater activity compared to controls when the left reinnervated index finger was used, but also when the left-hand little finger and the fingers of the right hand innervated by uninjured nerves were used. We argue that the overall increase in activity reflects a general disinhibition of contralesional S1 consistent with an augmented functional reorganizational plasticity being an ongoing feature of chronic recovery from nerve injury. Also, the nerve-injured showed increased activity within three prefrontal cortical areas implicated in higher-level behavioral processing (dorsal anterior cingulate cortex, left ventrolateral prefrontal and right dorsolateral prefrontal cortex), suggesting that processes supporting decision-making and response-selection were computationally more demanding due to the compromised tactile sensibility.

中文翻译：

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正中神经横断和神经再支配后人类初级躯体感觉皮层的去抑制作用

尽管采用了最先进的手术和术后治疗，但由于神经再支配能力的限制，正中神经横断会导致手部功能持续受损。有缺陷的神经支配以及受影响手的可控性会影响大脑对手动行为的控制。早期对触觉刺激处理变化的研究主要集中在对重新支配的手的刺激上，并且缺乏对大脑在感知方面对触觉输入的使用的充分控制。在这里，我们使用 fMRI 来测量 11 名正中神经损伤患者和健康对照组（N = 11）在使用任一手的食指或小指尖执行要求苛刻的触觉任务时的大脑活动（BOLD 信号）。对于神经损伤组，在研究前平均 8 年，左正中神经在前臂远端被创伤性横断并手术修复。当使用左手重新支配食指时，他们的对侧（右）初级躯体感觉皮层（S1）的手部表现比对照组表现出更大的活动，而且当左手小指和右手手指由未受伤的神经支配时也是如此被使用。我们认为，活动的整体增加反映了对侧 S1 的普遍去抑制与增强的功能重组可塑性是神经损伤慢性恢复的持续特征一致。此外，神经损伤的三个前额叶皮层区域的活动增加，与高级行为处理有关（背侧前扣带回皮层，