Radboud University Nijmegen, Donders Institute for Brain, Cognition, and Behaviour, Department of Biophysics, 6525 EZ Nijmegen, The Netherlands.
J Neurosci. 2011 Jul 20;31(29):10558-68. doi: 10.1523/JNEUROSCI.0998-11.2011.
How does the visuomotor system decide whether a target is moving or stationary in space or whether it moves relative to the eyes or head? A visual flash during a rapid eye-head gaze shift produces a brief visual streak on the retina that could provide information about target motion, when appropriately combined with eye and head self-motion signals. Indeed, double-step experiments have demonstrated that the visuomotor system incorporates actively generated intervening gaze shifts in the final localization response. Also saccades to brief head-fixed flashes during passive whole-body rotation compensate for vestibular-induced ocular nystagmus. However, both the amount of retinal motion to invoke spatial updating and the default strategy in the absence of detectable retinal motion remain unclear. To study these questions, we determined the contribution of retinal motion and the vestibular canals to spatial updating of visual flashes during passive whole-body rotation. Head- and body-restrained humans made saccades toward very brief (0.5 and 4 ms) and long (100 ms) visual flashes during sinusoidal rotation around the vertical body axis in total darkness. Stimuli were either attached to the chair (head-fixed) or stationary in space and were always well localizable. Surprisingly, spatial updating only occurred when retinal stimulus motion provided sufficient information: long-duration stimuli were always appropriately localized, thus adequately compensating for vestibular nystagmus and the passive head movement during the saccade reaction time. For the shortest stimuli, however, the target was kept in retinocentric coordinates, thus ignoring intervening nystagmus and passive head displacement, regardless of whether the target was moving with the head or not.
视动系统如何决定目标在空间中是移动还是静止的，或者它相对于眼睛或头部是如何移动的？在快速眼-头扫视过程中，闪光会在视网膜上产生短暂的光条纹，这可以提供有关目标运动的信息，当与眼睛和头部的自身运动信号适当结合时更是如此。事实上，双步实验已经证明，视动系统在最终的定位反应中主动纳入了主动产生的中间扫视。此外，在被动全身旋转过程中，朝向短暂的头部固定闪光的扫视可以补偿前庭引起的眼球震颤。然而，引起空间更新的视网膜运动的量以及在没有可检测到的视网膜运动时的默认策略仍不清楚。为了研究这些问题，我们确定了在被动全身旋转过程中，视网膜运动和前庭管对视觉闪光的空间更新的贡献。头和身体受限的人类在完全黑暗中，沿垂直身体轴进行正弦旋转时，向非常短暂（0.5 和 4 毫秒）和长（100 毫秒）的视觉闪光进行扫视。刺激物要么附着在椅子上（头部固定），要么在空间中静止，并且始终可以很好地定位。令人惊讶的是，只有当视网膜刺激运动提供了足够的信息时，空间更新才会发生：长持续时间的刺激总是被适当定位，从而充分补偿了前庭性眼球震颤和扫视反应时间期间的被动头部运动。然而，对于最短的刺激，目标仍保留在视网膜中心坐标中，从而忽略了中间的眼球震颤和被动头部位移，无论目标是否随头部移动。
