Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Str. 2, 82152, Planegg, Germany.
Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University Munich, Großhaderner Str. 2, 82152, Planegg, Germany.
J Neurol. 2023 Jan;270(1):57-70. doi: 10.1007/s00415-022-11311-8. Epub 2022 Aug 10.
Visual image motion-driven ocular motor behaviors such as the optokinetic reflex (OKR) provide sensory feedback for optimizing gaze stability during head/body motion. The performance of this visuo-motor reflex is subject to plastic alterations depending on requirements imposed by specific eco-physiological or developmental circumstances. While visuo-motor plasticity can be experimentally induced by various combinations of motion-related stimuli, the extent to which such evoked behavioral alterations contribute to the behavioral demands of an environment remains often obscure. Here, we used isolated preparations of Xenopus laevis tadpoles to assess the extent and ontogenetic dependency of visuo-motor plasticity during prolonged visual image motion. While a reliable attenuation of large OKR amplitudes can be induced already in young larvae, a robust response magnitude-dependent bidirectional plasticity is present only at older developmental stages. The possibility of older larvae to faithfully enhance small OKR amplitudes coincides with the developmental maturation of inferior olivary-Purkinje cell signal integration. This conclusion was supported by the loss of behavioral plasticity following transection of the climbing fiber pathway and by the immunohistochemical demonstration of a considerable volumetric extension of the Purkinje cell dendritic area between the two tested stages. The bidirectional behavioral alterations with different developmental onsets might functionally serve to standardize the motor output, comparable to the known differential adaptability of vestibulo-ocular reflexes in these animals. This homeostatic plasticity potentially equilibrates the working range of ocular motor behaviors during altered visuo-vestibular conditions or prolonged head/body motion to fine-tune resultant eye movements.
视觉图像运动驱动的眼球运动行为，如视动反射（OKR），为头部/身体运动期间优化注视稳定性提供了感觉反馈。这种视动反射的性能受到可塑性改变的影响，具体取决于特定生态生理或发育情况所施加的要求。虽然视动可塑性可以通过各种运动相关刺激的组合来实验性地诱导，但这种诱发的行为改变在多大程度上有助于环境的行为需求仍然常常不清楚。在这里，我们使用非洲爪蟾幼体的分离标本来评估长时间视觉图像运动期间视动可塑性的程度和个体发育依赖性。虽然在幼体中已经可以可靠地诱导大 OKR 幅度的衰减，但只有在较老的发育阶段才存在响应幅度相关的双向可塑性。大龄幼虫能够真实地增强小 OKR 幅度的可能性与下橄榄核-浦肯野细胞信号整合的发育成熟相吻合。这一结论得到了以下证据的支持：切断攀附纤维通路后，行为可塑性丧失，以及在两个测试阶段之间浦肯野细胞树突区域的体积显著扩展的免疫组织化学证明。具有不同发育起始的双向行为改变可能在功能上起到标准化运动输出的作用，类似于这些动物中前庭眼反射的已知差异适应性。这种同型可塑性可能会在改变的视-前庭条件或长时间头部/身体运动期间平衡眼球运动行为的工作范围，以微调产生的眼球运动。
