Institute for Psychology & Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany.
IMPACT Team, Lyon Neuroscience Research Center, University Claude Bernard Lyon 1, Bron cedex, France.
PLoS Comput Biol. 2023 Aug 4;19(8):e1011322. doi: 10.1371/journal.pcbi.1011322. eCollection 2023 Aug.
The cerebellum implements error-based motor learning via synaptic gain adaptation of an inverse model, i.e. the mapping of a spatial movement goal onto a motor command. Recently, we modeled the motor and perceptual changes during learning of saccadic eye movements, showing that learning is actually a threefold process. Besides motor recalibration of (1) the inverse model, learning also comprises perceptual recalibration of (2) the visuospatial target map and (3) of a forward dynamics model that estimates the saccade size from corollary discharge. Yet, the site of perceptual recalibration remains unclear. Here we dissociate cerebellar contributions to the three stages of learning by modeling the learning data of eight cerebellar patients and eight healthy controls. Results showed that cerebellar pathology restrains short-term recalibration of the inverse model while the forward dynamics model is well informed about the reduced saccade change. Adaptation of the visuospatial target map trended in learning direction only in control subjects, yet without reaching significance. Moreover, some patients showed a tendency for uncompensated oculomotor fatigue caused by insufficient upregulation of saccade duration. According to our model, this could induce long-term perceptual compensation, consistent with the overestimation of target eccentricity found in the patients' baseline data. We conclude that the cerebellum mediates short-term adaptation of the inverse model, especially by control of saccade duration, while the forward dynamics model was not affected by cerebellar pathology.
小脑通过逆模型的突触增益适应来实现基于错误的运动学习，即空间运动目标到运动指令的映射。最近，我们对眼球运动学习过程中的运动和知觉变化进行了建模，表明学习实际上是一个三重过程。除了（1）逆模型的运动重新校准外，学习还包括（2）视觉空间目标图和（3）从伴随放电估计扫视大小的前向动力学模型的知觉重新校准。然而，知觉重新校准的部位仍不清楚。在这里，我们通过对 8 名小脑患者和 8 名健康对照者的学习数据进行建模，来区分小脑对学习三个阶段的贡献。结果表明，小脑病变限制了逆模型的短期重新校准，而前向动力学模型很好地了解了减少的扫视变化。在控制受试者中，视觉空间目标图的适应仅在学习方向上呈趋势，但没有达到显著水平。此外，一些患者由于扫视持续时间的上调不足而表现出未补偿的眼球运动疲劳趋势。根据我们的模型，这可能会导致长期的知觉补偿，与患者基线数据中发现的目标偏心率高估一致。我们得出结论，小脑介导逆模型的短期适应，特别是通过控制扫视持续时间，而前向动力学模型不受小脑病变的影响。
