Effect of spinal cord injury on neural encoding of spontaneous postural perturbations in the hindlimb sensorimotor cortex
Effect of spinal cord injury on neural encoding of spontaneous postural perturbations in the hindlimb sensorimotor cortex
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DOI：
10.1152/jn.00727.2020
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发表时间：
2021-11-01
影响因子：
2.5
通讯作者：
Moxon, Karen A.
中科院分区：
文献类型：
--
作者：
Dougherty, Jaimie B.;Disse, Gregory D.;Moxon, Karen A.
棘上信号在姿势扰动的代偿反应中起重要作用。虽然皮质对于完整动物的基本姿势任务不是必需的，但其在脊髓损伤（SCI）后对意外姿势扰动的反应中的作用尚未研究。为了更好地理解SCI如何影响姿势扰动的皮层编码，在大鼠中记录了后肢感觉运动皮层（HLSMC）中单个神经元在完全胸中部脊髓横断前后的意外倾斜期间的活动。在一个动物亚组中，还收集了肢体地面反作用力。HLSMC活性强烈调制响应于不同的倾斜配置文件。随着倾斜速度的增加，HLSMC神经元传达了更多关于扰动的信息，这是由于招募的神经元数量和它们的响应幅度都增加了。脊髓损伤导致后肢地面反应力减弱和延迟。然而，HLSMC神经元仍然对损伤后的倾斜反应，但增加了延迟和减少调谐到较慢的倾斜。因此，SCI后皮层神经元传递的关于倾斜的信息减少了，需要更多的细胞来传递与横断前相同数量的信息。考虑到完全胸中段脊髓损伤后，后肢感觉运动皮层的重组对治疗的反应是行为恢复所必需的，SCI后持续的信息编码可能是重组的基础，利用来自损伤上方的感觉信息来控制躯干肌肉，从而允许重量支撑的行走和姿势控制。值得注意的是，皮层回路在姿势和平衡编码中的作用对于开发脊髓损伤的治疗方法很有意义。这项工作表明，意想不到的姿势扰动编码在后肢感觉运动皮层，即使在没有后肢感觉反馈。事实上，后肢感觉运动皮层在脊髓完全横断后继续编码姿势扰动。
Supraspinal signals play a significant role in compensatory responses to postural perturbations. Although the cortex is not necessary for basic postural tasks in intact animals, its role in responding to unexpected postural perturbations after spinal cord injury (SCI) has not been studied. To better understand how SCI impacts cortical encoding of postural perturbations, the activity of single neurons in the hindlimb sensorimotor cortex (HLSMC) was recorded in the rat during unexpected tilts before and after a complete midthoracic spinal transection. In a subset of animals, limb ground reaction forces were also collected. HLSMC activity was strongly modulated in response to different tilt profiles. As the velocity of the tilt increased, more information was conveyed by the HLSMC neurons about the perturbation due to increases in both the number of recruited neurons and the magnitude of their responses. SCI led to attenuated and delayed hindlimb ground reaction forces. However, HLSMC neurons remained responsive to tilts after injury but with increased latencies and decreased tuning to slower tilts. Information conveyed by cortical neurons about the tilts was therefore reduced after SCI, requiring more cells to convey the same amount of information as before the transection. Given that reorganization of the hindlimb sensorimotor cortex in response to therapy after complete midthoracic SCI is necessary for behavioral recovery, this sustained encoding of information after SCI could be a substrate for the reorganization that uses sensory information from above the lesion to control trunk muscles that permit weight-supported stepping and postural control.NEW & NOTEWORTHY The role of cortical circuits in the encoding of posture and balance is of interest for developing therapies for spinal cord injury. This work demonstrated that unexpected postural perturbations are encoded in the hindlimb sensorimotor cortex even in the absence of hindlimb sensory feedback. In fact, the hindlimb sensorimotor cortex continues to encode for postural perturbations after complete spinal transection.