Hodgson Timothy Lewis, Golding Charlotte, Molyva Dimitra, Rosenthal Clive R, Kennard Christopher
Washington Singer Laboratories, School of Psychology, University of Exeter, UK.
J Cogn Neurosci. 2004 Mar;16(2):318-30. doi: 10.1162/089892904322984599.
Active vision is a dynamic process involving the flexible coordination of different gaze strategies to achieve behavioral goals. Although many complex behaviors rely on an ability to efficiently switch between gaze-control strategies, few studies to date have examined mechanisms of task level oculomotor control in detail. Here, we report five experiments in which subjects alternated between conflicting stimulus-saccade mappings within a block of trials. The first experiment showed that there is no performance cost associated with switching between pro and anti saccades. However, follow-up experiments demonstrate that whenever subjects alternate between arbitrary stimulus-saccade mappings, latency costs are apparent on the first trial after a task change. More detailed analysis of switch costs showed that latencies were particularly elevated for saccades directed toward the same location that had been the target for a saccade on the preceeding trial. This saccade "inhibition of return" effect was most marked when unexpected error feedbacks cued task switches, suggesting that saccade selection processes are modulated by reward. We conclude that there are two systems for saccade control that differ in their characteristics following a task switch. The "reflexive" control system can be enabled/disabled in advance of saccade execution without incurring any performance cost. Switch costs are only observed when two or more arbitrary stimulus-saccade mappings have to be coordinated by a "symbolic" control system.
主动视觉是一个动态过程，涉及不同注视策略的灵活协调以实现行为目标。尽管许多复杂行为依赖于在注视控制策略之间有效切换的能力，但迄今为止很少有研究详细考察任务水平眼动控制的机制。在此，我们报告了五个实验，实验中被试在一组试验中交替进行冲突的刺激 - 扫视映射。第一个实验表明，在顺向和逆向扫视之间切换不存在行为代价。然而，后续实验表明，每当被试在任意刺激 - 扫视映射之间交替时，任务改变后的第一次试验中潜伏期代价就很明显。对切换代价的更详细分析表明，对于指向与前一次试验中扫视目标相同位置的扫视，潜伏期尤其延长。当意外的错误反馈提示任务切换时，这种扫视“返回抑制”效应最为明显，这表明扫视选择过程受奖励调节。我们得出结论，在任务切换后，有两种扫视控制系统，其特征有所不同。“反射性”控制系统可以在扫视执行前启用/禁用，而不会产生任何行为代价。只有当两个或更多任意刺激 - 扫视映射必须由“符号性”控制系统协调时，才会观察到切换代价。
