Data from: Vision fine-tunes preparation for landing in the cane toad, Rhinella marina

In toad hopping, the hindlimbs generate the propulsive force for takeoff while the forelimbs resist the impact forces associated with landing. Preparing to perform a safe landing, in which impact forces are managed appropriately, likely involves the integration of multiple types of sensory feedback. In toads, vestibular and/or proprioceptive feedback are critical for coordinated landing, however, the role of vision remains unclear. To clarify this role, this study compares pre-landing forelimb muscle activation patterns in animals before and after removing vision. Specifically, we recorded EMG activity from two antagonistic forelimb muscles, the anconeus and coracoradialis, which demonstrate distance-dependent onset timing and recruitment intensity, respectively. Toads were first recorded hopping normally and then again after their optic nerves were severed to remove visual feedback. When blind, toads exhibited basic hop kinematics and pre-landing muscle activity similar to when sighted. However, distance-dependent relationships for muscle activity patterns were more variable, if present at all. This study demonstrates that blind toads are still able to perform coordinated landings, reinforcing the importance of proprioceptive and/or vestibular feedback during hopping. But the increased variability in distance-dependent activity patterns indicates that vision is more responsible for fine-tuning the motor control strategy for landing.

在蟾蜍跳跃过程中，后肢为起跳提供推进力，而前肢则用于抵消落地过程中产生的冲击力。要实现冲击力管控得当的安全落地，往往需要整合多种类型的感觉反馈（sensory feedback）。对于蟾蜍而言，前庭反馈（vestibular feedback）和/或本体感受反馈（proprioceptive feedback）对协调落地至关重要，但视觉在此过程中所扮演的角色仍未明确。为阐明视觉的具体作用，本研究对比了蟾蜍去除视觉前后的落地前前肢肌肉激活模式。具体而言，我们记录了两组拮抗前肢肌肉——肘肌（anconeus）和喙桡肌（coracoradialis）——的肌电图（electromyography, EMG）活动，二者分别表现出与距离相关的激活时序和募集强度。实验首先记录蟾蜍正常跳跃时的肌电活动，随后通过切断视神经以移除视觉反馈，再次开展记录。失明后的蟾蜍，其基本跳跃运动学（kinematics）特征与落地前肌肉激活模式，均与具备视觉时相似。但即便其肌肉活动模式仍存在与距离相关的关联，该关联的变异性也显著提升。本研究证明，失明蟾蜍仍可完成协调的落地动作，这进一步印证了跳跃过程中本体感受和/或前庭反馈的重要性。但肌肉活动模式的距离相关性所呈现出的变异性升高现象，则表明视觉更多承担着对落地运动控制策略进行精细调节的功能。