Supraspinal signals play a significant role in compensatory responses to postural perturbations. While 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 mid-thoracic 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.

中文翻译：

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脊髓损伤对后肢感觉运动皮层自发姿势扰动神经编码的影响


脊柱上信号在对姿势扰动的补偿反应中发挥着重要作用。虽然皮层对于完整动物的基本姿势任务不是必需的，但其在应对脊髓损伤（SCI）后意外姿势扰动中的作用尚未研究。为了更好地了解 SCI 如何影响姿势扰动的皮层编码，在完全中胸脊柱横断前后意外倾斜期间，记录了大鼠后肢感觉运动皮层 (HLSMC) 中单个神经元的活动。在一部分动物中，还收集了肢体地面反作用力。 HLSMC 活动受到不同倾斜剖面的强烈调节。随着倾斜速度的增加，由于招募的神经元数量及其反应强度的增加，HLSMC 神经元传递了更多有关扰动的信息。 SCI 导致后肢地面反作用力减弱和延迟。然而，HLSMC 神经元在受伤后仍然对倾斜有反应，但延迟增加，对较慢倾斜的调节减少。因此，SCI 后皮质神经元传递的有关倾斜的信息减少，需要更多的细胞传递与横断前相同数量的信息。鉴于完全中胸脊髓损伤后，后肢感觉运动皮层响应治疗的重组对于行为恢复是必要的，脊髓损伤后这种持续的信息编码可能成为利用来自病变上方的感觉信息来控制躯干肌肉的重组的基础允许重量支撑的迈步和姿势控制。