Does Ipsilateral Remapping Following Hand Loss Impact Motor Control of the Intact Hand?
Does Ipsilateral Remapping Following Hand Loss Impact Motor Control of the Intact Hand?
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DOI：
10.1523/jneurosci.0948-23.2023
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发表时间：
2023-05
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影响因子：
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通讯作者：
Raffaele Tucciarelli;N. Ejaz;D. B. Wesselink;Vijay Kolli;Carl J. Hodgetts;J. Diedrichsen;T. Makin
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作者：
Raffaele Tucciarelli;N. Ejaz;D. B. Wesselink;Vijay Kolli;Carl J. Hodgetts;J. Diedrichsen;T. Makin
一旦皮层区域变得功能冗余，会发生什么？我们研究了人类（男性和女性）的大脑功能和行为的变化，无论是从出生（单手）或由于截肢失去了一只手。以前的研究报告说，截肢者，但不是单手，显示增加同侧活动的躯体感觉领域的失踪的手（即，重新映射）。我们使用了一个复杂的手指任务，以探讨是否在截肢者中观察到的重新映射涉及招募更多的神经资源，以支持完整的手，以满足更大的运动控制需求。使用基本的功能磁共振成像分析，我们发现，只有截肢者有更多的同侧活动时，运动需求增加;然而，这并不匹配任何明显的改善，他们的行为任务的表现。更先进的多变量功能磁共振成像分析表明，截肢者有更强和更典型的代表-相对于对照组的对侧手的代表-与单手。这表明在截肢者中，双手区域更协同地工作，可能反映了完整手的传出复制。单手努力学习困难的手指配置，但这并没有转化为单变量或多变量活动相对于对照组的差异。额外的白色物质分析提供了确凿的证据，表明两个手部区域之间的结构连接性在各组之间没有变化。总之，我们的研究结果表明，增强活动在失踪的手领土可能并不反映完整的手功能。相反，我们认为，可塑性比一般认为的更受限制，可能取决于生命早期获得的同源通路的可用性。
What happens once a cortical territory becomes functionally redundant? We studied changes in brain function and behavior for the remaining hand in humans (male and female) with either a missing hand from birth (one-handers) or due to amputation. Previous studies reported that amputees, but not one-handers, show increased ipsilateral activity in the somatosensory territory of the missing hand (i.e., remapping). We used a complex finger task to explore whether this observed remapping in amputees involves recruiting more neural resources to support the intact hand to meet greater motor control demands. Using basic fMRI analysis, we found that only amputees had more ipsilateral activity when motor demand increased; however, this did not match any noticeable improvement in their behavioral task performance. More advanced multivariate fMRI analyses showed that amputees had stronger and more typical representation—relative to controls’ contralateral hand representation—compared with one-handers. This suggests that in amputees, both hand areas work together more collaboratively, potentially reflecting the intact hand's efference copy. One-handers struggled to learn difficult finger configurations, but this did not translate to differences in univariate or multivariate activity relative to controls. Additional white matter analysis provided conclusive evidence that the structural connectivity between the two hand areas did not vary across groups. Together, our results suggest that enhanced activity in the missing hand territory may not reflect intact hand function. Instead, we suggest that plasticity is more restricted than generally assumed and may depend on the availability of homologous pathways acquired early in life.