Ramkumar Pavan, Fernandes Hugo, Kording Konrad, Segraves Mark
Department of Physical Medicine and Rehabilitation, Northwestern University and Rehabilitation Institute of Chicago, Chicago, IL, USA Department of Neurobiology, Northwestern University, Evanston, IL, USA.
Department of Physical Medicine and Rehabilitation, Northwestern University and Rehabilitation Institute of Chicago, Chicago, IL, USA Instituto Gulbenkian de Ciência, Oeiras, Portugal.
J Vis. 2015 Mar 26;15(3):19. doi: 10.1167/15.3.19.
Like humans, monkeys make saccades nearly three times a second. To understand the factors guiding this frequent decision, computational models of vision attempt to predict fixation locations using bottom-up visual features and top-down goals. How do the relative influences of these factors evolve over multiple time scales? Here we analyzed visual features at fixations using a retinal transform that provides realistic visual acuity by suitably degrading visual information in the periphery. In a task in which monkeys searched for a Gabor target in natural scenes, we characterized the relative importance of bottom-up and task-relevant influences by decoding fixated from nonfixated image patches based on visual features. At fast time scales, we found that search strategies can vary over the course of a single trial, with locations of higher saliency, target-similarity, edge–energy, and orientedness looked at later on in the trial. At slow time scales, we found that search strategies can be refined over several weeks of practice, and the influence of target orientation was significant only in the latter of two search tasks. Critically, these results were not observed without applying the retinal transform. Our results suggest that saccade-guidance strategies become apparent only when models take into account degraded visual representation in the periphery.
与人类一样，猴子每秒会进行近三次扫视。为了理解引导这一频繁决策的因素，视觉计算模型试图利用自下而上的视觉特征和自上而下的目标来预测注视位置。这些因素的相对影响在多个时间尺度上是如何演变的？在这里，我们使用一种视网膜变换来分析注视点处的视觉特征，该变换通过适当地降低周边视觉信息的质量来提供逼真的视觉敏锐度。在一项猴子在自然场景中搜索Gabor目标的任务中，我们通过基于视觉特征从未注视的图像块中解码注视点，来表征自下而上和与任务相关的影响的相对重要性。在快速时间尺度上，我们发现搜索策略在单次试验过程中可能会发生变化，在试验后期会看向显著性更高、目标相似度更高、边缘能量更高和定向性更强的位置。在缓慢时间尺度上，我们发现搜索策略可以在几周的练习中得到优化，并且目标方向的影响仅在两个搜索任务中的后者中显著。至关重要的是，如果不应用视网膜变换，就不会观察到这些结果。我们的结果表明，只有当模型考虑到周边视觉表征的退化时，扫视引导策略才会变得明显。
