Canaveral Cesar Augusto, Danion Frédéric, Berrigan Félix, Bernier Pierre-Michel
Département de kinanthropologie, Faculté des sciences de l'activité physique, Université de Sherbrooke, Sherbrooke, Québec, Canada; and.
Aix-Marseille Université, CNRS, Institut de Neurosciences de la Timone, Marseille, France.
J Neurophysiol. 2017 Nov 1;118(5):2745-2754. doi: 10.1152/jn.00416.2017. Epub 2017 Aug 16.
Sensorimotor control requires an accurate estimate of the state of the body. The brain optimizes state estimation by combining sensory signals with predictions of the sensory consequences of motor commands using a forward model. Given that both sensory signals and predictions are uncertain (i.e., noisy), the brain optimally weights the relative reliance on each source of information during adaptation. In support, it is known that uncertainty in the sensory predictions influences the rate and generalization of visuomotor adaptation. We investigated whether uncertainty in the sensory predictions affects the retention of a new visuomotor relationship. This was done by exposing three separate groups to a visuomotor rotation whose mean was common at 15° counterclockwise but whose variance around the mean differed (i.e., SD of 0°, 3.2°, or 4.5°). Retention was assessed by measuring the persistence of the adapted behavior in a no-vision phase. Results revealed that mean reach direction late in adaptation was similar across groups, suggesting it depended mainly on the mean of exposed rotations and was robust to differences in variance. However, retention differed across groups, with higher levels of variance being associated with a more rapid reversion toward nonadapted behavior. A control experiment ruled out the possibility that differences in retention were accounted for by differences in success rates. Exposure to variable rotations may have increased the uncertainty in sensory predictions, making the adapted forward model more labile and susceptible to change or decay. The brain predicts the sensory consequences of motor commands through a forward model. These predictions are subject to uncertainty. We use visuomotor adaptation and modulate uncertainty in the sensory predictions by manipulating the variance in exposed rotations. Results reveal that variance does not influence the final extent of adaptation but selectively impairs the retention of motor memories. These results suggest that a more uncertain forward model is more susceptible to change or decay.
感觉运动控制需要对身体状态进行准确估计。大脑通过使用前向模型将感觉信号与运动命令的感觉后果预测相结合，来优化状态估计。鉴于感觉信号和预测都是不确定的（即有噪声），大脑在适应过程中会对依赖每个信息源的相对权重进行最优分配。有证据支持的是，感觉预测中的不确定性会影响视觉运动适应的速率和泛化。我们研究了感觉预测中的不确定性是否会影响新的视觉运动关系的保持。这是通过将三个独立的组暴露于一个视觉运动旋转来完成的，该旋转的平均值在逆时针15°时是相同的，但围绕平均值的方差不同（即标准差为0°、3.2°或4.5°）。通过测量无视觉阶段适应行为的持续性来评估保持情况。结果显示，在适应后期，各组的平均伸手方向相似，这表明它主要取决于所暴露旋转的平均值，并且对方差的差异具有鲁棒性。然而，各组的保持情况不同，方差水平越高，与向未适应行为更快逆转相关。一项对照实验排除了保持差异是由成功率差异所解释的可能性。暴露于可变旋转可能增加了感觉预测中的不确定性，使适应的前向模型更不稳定且更容易发生变化或衰退。大脑通过前向模型预测运动命令的感觉后果。这些预测存在不确定性。我们利用视觉运动适应，并通过操纵所暴露旋转中的方差来调节感觉预测中的不确定性。结果表明，方差并不影响最终的适应程度，但会选择性地损害运动记忆的保持。这些结果表明，更不确定的前向模型更容易发生变化或衰退。
