Department of Human Physiology, University of Oregon, Eugene, OR, USA.
Department of Human Physiology, University of Oregon, Eugene, OR, USA.
Neuroimage Clin. 2023;39:103499. doi: 10.1016/j.nicl.2023.103499. Epub 2023 Aug 18.
It is becoming increasingly clear that limb loss induces wider spread reorganization of representations of the body that are nonadjacent to the affected cortical territory. Data from upper extremity amputees reveal intrusion of the representation of the ipsilateral intact limb into the former hand territory. Here we test for the first time whether this reorganization of the intact limb into the deprived cortex is specific to the neurological organization of the upper limbs or reflects large scale adaptation that is triggered by any unilateral amputation. BOLD activity was measured as human subjects with upper limb and lower limb traumatic amputation and their controls moved the toes on each foot, open and closed each hand and pursed their lips. Subjects with amputation were asked to imagine moving the missing limb while remaining still. Bayesian pattern component modeling of fMRI data showed that intact ipsilateral movements and contralateral movements of the hand and foot were distinctly represented in the deprived sensorimotor cortex years after upper limb amputation. In contrast, there was evidence reminiscent of contralateral specificity for hand and foot movements following lower limb amputation, like that seen in controls. We propose the cortical reorganization of the intact limb to be a function of use-dependent plasticity that is more specific to the consequence of upper limb loss of forcing an asymmetric reliance on the intact hand and arm. The contribution of this reorganization to phantom pain or a heightened risk of overuse and resultant maladaptive plasticity needs investigating before targeting such reorganization in intervention.
肢体丧失会引起身体代表区域的广泛重组，这些区域与受影响的皮质区域不相邻，这一点越来越明显。来自上肢截肢者的数据显示，同侧完整肢体的代表区域侵入了以前的手部区域。在这里，我们首次测试了这种对完整肢体的重组是否是特定于上肢的神经组织，还是反映了由任何单侧截肢引发的大规模适应。当人类受试者进行上肢和下肢创伤性截肢及其对照者移动每个脚的脚趾、张开和关闭每个手以及撅起嘴唇时，我们测量了 BOLD 活性。要求截肢者在保持静止的情况下想象缺失的肢体运动。fMRI 数据的贝叶斯模式成分建模显示，在失去上肢多年后，未受影响的感觉运动皮质中清晰地代表了完整的同侧运动和对侧手和脚的运动。相比之下，下肢截肢后，手和脚的运动有证据表明类似于对照者的对侧特异性。我们提出，完整肢体的皮质重组是一种依赖于使用的可塑性的功能，它更特定于上肢丧失的后果，即迫使对手和手臂的不对称依赖。在干预中针对这种重组之前，需要研究这种重组对手部幻觉痛或过度使用和由此产生的适应性不良的风险增加的贡献。
