Bernstein Center for Computational Neuroscience Berlin, Charité - Universitätsmedizin Berlin, 10115 Berlin, Germany.
Curr Biol. 2011 Oct 11;21(19):1667-71. doi: 10.1016/j.cub.2011.08.039. Epub 2011 Sep 29.
An important requirement for vision is to identify interesting and relevant regions of the environment for further processing. Some models assume that salient locations from a visual scene are encoded in a dedicated spatial saliency map [1, 2]. Then, a winner-take-all (WTA) mechanism [1, 2] is often believed to threshold the graded saliency representation and identify the most salient position in the visual field. Here we aimed to assess whether neural representations of graded saliency and the subsequent WTA mechanism can be dissociated. We presented images of natural scenes while subjects were in a scanner performing a demanding fixation task, and thus their attention was directed away. Signals in early visual cortex and posterior intraparietal sulcus (IPS) correlated with graded saliency as defined by a computational saliency model. Multivariate pattern classification [3, 4] revealed that the most salient position in the visual field was encoded in anterior IPS and frontal eye fields (FEF), thus reflecting a potential WTA stage. Our results thus confirm that graded saliency and WTA-thresholded saliency are encoded in distinct neural structures. This could provide the neural representation required for rapid and automatic orientation toward salient events in natural environments.
视觉的一个重要要求是识别环境中有趣和相关的区域，以便进一步处理。一些模型假设视觉场景中的显著位置是在专门的空间显著图中编码的[1,2]。然后，通常认为竞争选择（WTA）机制[1,2]会对渐变显著度表示进行阈值处理，并确定视野中最显著的位置。在这里，我们旨在评估渐变显著度的神经表示和随后的 WTA 机制是否可以分离。当受试者在扫描仪中执行一项要求很高的注视任务时，我们呈现自然场景的图像，因此他们的注意力被转移开了。早期视觉皮层和后顶内沟（IPS）的信号与计算显著性模型定义的渐变显著性相关。多元模式分类[3,4]显示，视野中最显著的位置被编码在前 IPS 和额眼区（FEF）中，因此反映了潜在的 WTA 阶段。我们的结果因此证实了渐变显著度和 WTA 阈值显著度是在不同的神经结构中编码的。这可能为在自然环境中快速自动朝向显著事件提供所需的神经表示。
