Bennett Simon J, Orban de Xivry Jean-Jacques, Barnes Graham R, Lefèvre Philippe
Research Institute for Exercise and Sport Sciences, Liverpool John Moores University, Henry Cotton Campus, L3 2ET, Liverpool, UK.
J Neurophysiol. 2007 Sep;98(3):1405-14. doi: 10.1152/jn.00132.2007. Epub 2007 Jun 6.
Given sufficient exposure to stimulus presentation, the oculomotor system generates a representation of the stimulus characteristics, which is then used to predict the upcoming target motion. In addition to compensating for the perceptual-motor delay, these predictive processes perpetuate eye motion during a transient occlusion and compensate for the loss of visual input. At present, however, it is not well understood whether and how the oculomotor system extracts and represents target acceleration for subsequent predictive control. To this end, we used a target occlusion paradigm where both position and velocity of the target during the occlusion and at reappearance could not be predicted without extracting target acceleration before target disappearance. We found that the oculomotor response during the blanking period was not influenced by target acceleration when the initial exposure was 200 ms. However, smooth and saccadic eye movements did discriminate between the different levels of acceleration after an initial 500- or 800-ms exposure. In the event that the smooth response during the occlusion did not match well the target trajectory and thus eliminate a developing displacement error, there was an increased saccadic displacement. Still, the combined response during the blanking period did not eliminate retinal slip and position error at target reappearance. These results indicate that information on target acceleration can be extracted on-line, during pursuit of a visible ramp, and then used to drive a predictive oculomotor response in the absence of visual input.
在有足够的刺激呈现暴露的情况下,动眼系统会生成刺激特征的表征,然后用于预测即将到来的目标运动。除了补偿感知运动延迟外,这些预测过程还能在短暂遮挡期间使眼球运动持续,并补偿视觉输入的损失。然而,目前尚不清楚动眼系统是否以及如何提取和表征目标加速度以进行后续的预测控制。为此,我们采用了一种目标遮挡范式,在这种范式中,如果在目标消失前不提取目标加速度,就无法预测遮挡期间和重新出现时目标的位置和速度。我们发现,当初始暴露时间为200毫秒时,消隐期的动眼反应不受目标加速度的影响。然而,在初始暴露500毫秒或800毫秒后,平滑和扫视眼球运动确实能区分不同水平的加速度。如果遮挡期间的平滑反应与目标轨迹匹配不佳,从而无法消除逐渐增大的位移误差,那么扫视位移就会增加。尽管如此,消隐期的综合反应在目标重新出现时并未消除视网膜滑动和位置误差。这些结果表明,在追踪可见斜坡期间,可以在线提取目标加速度信息,然后在没有视觉输入的情况下用于驱动预测性动眼反应。