Bao Min, Fast Elizabeth, Mesik Juraj, Engel Stephen
Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, P.R. China.
J Vis. 2013 Aug 26;13(10):14. doi: 10.1167/13.10.14.
Changes to the visual environment can happen at many timescales, from very transient to semi-permanent. To adapt optimally, the visual system also adjusts at different timescales, with longer-lasting environmental changes producing longer-lasting effects, but how the visual system adapts in this way remains unknown. Here, we show that contrast adaptation-the most-studied form of visual adaptation-has multiple controllers, each operating over a different time scale. In a series of experiments, subjects completed either a contrast matching, contrast detection, or tilt adjustment task, while adapting to contrast at one orientation. Following a relatively longer period (5 min) of adaptation to high contrast, subjects were "deadapted" for a shorter period (e.g., 40 s) to a lower contrast. Deadaptation eliminated perceptual aftereffects of adaptation, but continued testing in a neutral environment revealed their striking recovery. These results suggest the following account: Adaptation was controlled by at least two mechanisms, with initial adaptation affecting a longer-term one and deadaptation affecting a shorter-term one in the opposite direction. Immediately following deadaptation, the effects of the two mechanisms cancelled each other, but the short-term effects rapidly decayed, revealing ongoing longer-term adaptation. A single controlling mechanism cannot account for the observed recovery of effects, since once deadaptation cancels the initial longer-term adaptation, no trace of it remains. Combined with previous results at very long adaptation durations, the present results suggest that contrast adaptation is possibly controlled by a continuum of mechanisms acting over a large range of timescales.
视觉环境的变化可以在许多时间尺度上发生，从非常短暂到半永久性。为了实现最佳适应，视觉系统也会在不同的时间尺度上进行调整，环境变化持续时间越长，产生的影响就越持久，但视觉系统如何以这种方式进行适应仍然未知。在这里，我们表明，对比度适应——视觉适应中研究最多的形式——有多个控制器，每个控制器在不同的时间尺度上运行。在一系列实验中，受试者完成对比度匹配、对比度检测或倾斜调整任务，同时适应一个方向的对比度。在对高对比度进行相对较长时间（5分钟）的适应后，受试者在较短时间（例如40秒）内适应较低对比度以“消除适应”。消除适应消除了适应的感知后效，但在中性环境中继续测试显示它们惊人地恢复了。这些结果表明如下情况：适应由至少两种机制控制，初始适应影响一种长期机制，而消除适应以相反方向影响一种短期机制。在消除适应后立即，两种机制的效果相互抵消，但短期效果迅速衰减，揭示了持续的长期适应。单一的控制机制无法解释观察到的效果恢复，因为一旦消除适应取消了初始的长期适应，就不会留下任何痕迹。结合之前在非常长的适应持续时间下的结果，目前的结果表明对比度适应可能由一系列在大范围时间尺度上起作用的机制控制。
