Porat Yuval, Zohary Ehud
The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Department of Neurobiology, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Proc Natl Acad Sci U S A. 2016 Nov 15;113(46):E7327-E7336. doi: 10.1073/pnas.1607051113. Epub 2016 Nov 2.
Visual sensitivity is markedly reduced during an eye movement. Peri-saccadic vision is also characterized by a mislocalization of the briefly presented stimulus closer to the saccadic target. These features are commonly viewed as obligatory elements of peri-saccadic vision. However, practice improves performance in many perceptual tasks performed at threshold conditions. We wondered if this could also be the case with peri-saccadic perception. To test this, we used a paradigm in which subjects reported the orientation (or location) of an ellipse briefly presented during a saccade. Practice on peri-saccadic orientation discrimination led to long-lasting gains in that task but did not alter the classical mislocalization of the visual stimulus. Shape discrimination gains were largely generalized to other untrained conditions when the same stimuli were used (discrimination during a saccade in the opposite direction or at a different stimulus location than previously trained). However, performance dropped to baseline level when participants shifted to a novel Vernier discrimination task under identical saccade conditions. Furthermore, practice on the location task did not induce better stimulus localization or discrimination. These results suggest that the limited visual information available during a saccade may be better used with practice, possibly by focusing attention on the specific target features or a better readout of the available information. Saccadic mislocalization, by contrast, is robust and resistant to top-down modulations, suggesting that it involves an automatic process triggered by the upcoming execution of a saccade (e.g., an efference copy signal).
在眼球运动期间，视觉敏感度会显著降低。扫视周围视觉的特点还包括，短暂呈现的刺激会被错误定位于更靠近扫视目标的位置。这些特征通常被视为扫视周围视觉的必然要素。然而，练习可以提高在阈值条件下执行的许多感知任务的表现。我们想知道扫视周围感知是否也是如此。为了测试这一点，我们采用了一种范式，让受试者报告在扫视过程中短暂呈现的椭圆的方向（或位置）。扫视周围方向辨别练习在该任务中带来了持久的进步，但并未改变视觉刺激的经典错误定位。当使用相同刺激时（与之前训练方向相反的扫视过程中的辨别或在与之前训练不同的刺激位置进行辨别），形状辨别进步在很大程度上可推广到其他未训练的条件。然而，当参与者在相同扫视条件下转向新的游标辨别任务时，表现降至基线水平。此外，位置任务的练习并未带来更好的刺激定位或辨别。这些结果表明，扫视过程中可用的有限视觉信息通过练习可能会得到更好的利用，可能是通过将注意力集中在特定目标特征上或更好地读取可用信息。相比之下，扫视错误定位是稳健的，且不受自上而下调制的影响，这表明它涉及由即将执行的扫视触发的自动过程（例如，传出副本信号）。
