Shafiq R, Stuart G W, Sandbach J, Maruff P, Currie J
Mental Health Research Institute of Victoria, Parkville, Australia.
Exp Brain Res. 1998 Jan;118(2):221-9. doi: 10.1007/s002210050275.
Latencies of eye movements to peripheral targets are reduced when there is a short delay (typically 200 ms) between the offset of a central visual fixation point and the target onset. This has been termed the gap effect. In addition, some subjects, usually with practice, exhibit a separate population of very short latency saccades, called express saccades. Both these phenomena have been attributed to disengagement of visual attention when the fixation point is extinguished. A competing theory of the gap effect attributes it to disengagement of oculomotor fixation during the temporal gap. It is known that auditory targets are effective in eliciting saccadic eye movements, and also that covert attention operates in the auditory modality. If the gap effect and express saccades are due to disengagement of spatial attention, both should persist in the auditory modality. However, fixation of gaze is largely under visual control. If the gap effect results from disengagement of fixation, then at least a reduced effect should be seen in the auditory modality. Human subjects performed the gap task and a control task in the dark, using auditory fixation points and saccadic targets, on five successive days. Despite this practice, express saccades were not observed. There was a reliable gap effect, but the reduction in saccadic latency was only 17 ms, compared with 32 ms for the same subjects in the visual modality. This suggests that about half the gap effect is due to disengagement of visual fixation. The remainder was not due to non-specific warning effects and could be attributed to offset of the auditory fixation stimulus.
当中央视觉注视点消失与外周目标出现之间存在短暂延迟（通常为200毫秒）时，眼动对外周目标的潜伏期会缩短。这一现象被称为间隙效应。此外，一些受试者（通常是经过练习的）会表现出另一类潜伏期极短的扫视，称为快速扫视。这两种现象都被归因于注视点消失时视觉注意力的脱离。一种关于间隙效应的竞争理论将其归因于时间间隙期间眼动注视的脱离。已知听觉目标能有效引发扫视眼动，并且隐蔽注意也在听觉模式中起作用。如果间隙效应和快速扫视是由于空间注意力的脱离，那么两者在听觉模式中都应持续存在。然而，注视主要受视觉控制。如果间隙效应是由注视的脱离导致的，那么在听觉模式中至少应观察到效应减弱。人类受试者在黑暗中连续五天使用听觉注视点和扫视目标执行间隙任务和对照任务。尽管有这样的练习，但未观察到快速扫视。存在可靠的间隙效应，但扫视潜伏期的缩短仅为17毫秒，而同一受试者在视觉模式下为32毫秒。这表明间隙效应约有一半是由于视觉注视的脱离。其余部分并非由于非特异性警告效应，可归因于听觉注视刺激的消失。
