Barbot Antoine, Landy Michael S, Carrasco Marisa
Department of Psychology, New York University, New York, NY, USA.
J Vis. 2012 Aug 15;12(8):6. doi: 10.1167/12/8/6.
The visual system can use a rich variety of contours to segment visual scenes into distinct perceptually coherent regions. However, successfully segmenting an image is a computationally expensive process. Previously we have shown that exogenous attention--the more automatic, stimulus-driven component of spatial attention--helps extract contours by enhancing contrast sensitivity for second-order, texture-defined patterns at the attended location, while reducing sensitivity at unattended locations, relative to a neutral condition. Interestingly, the effects of exogenous attention depended on the second-order spatial frequency of the stimulus. At parafoveal locations, attention enhanced second-order contrast sensitivity to relatively high, but not to low second-order spatial frequencies. In the present study we investigated whether endogenous attention-the more voluntary, conceptually-driven component of spatial attention--affects second-order contrast sensitivity, and if so, whether its effects are similar to those of exogenous attention. To that end, we compared the effects of exogenous and endogenous attention on the sensitivity to second-order, orientation-defined, texture patterns of either high or low second-order spatial frequencies. The results show that, like exogenous attention, endogenous attention enhances second-order contrast sensitivity at the attended location and reduces it at unattended locations. However, whereas the effects of exogenous attention are a function of the second-order spatial frequency content, endogenous attention affected second-order contrast sensitivity independent of the second-order spatial frequency content. This finding supports the notion that both exogenous and endogenous attention can affect second-order contrast sensitivity, but that endogenous attention is more flexible, benefitting performance under different conditions.
视觉系统可以利用丰富多样的轮廓将视觉场景分割成不同的、在感知上连贯的区域。然而，成功分割图像是一个计算成本高昂的过程。此前我们已经表明，外源性注意——空间注意中更具自动性、由刺激驱动的成分——通过增强对被关注位置处二阶纹理定义图案的对比敏感度，同时相对于中性条件降低未被关注位置处的敏感度，来帮助提取轮廓。有趣的是，外源性注意的效果取决于刺激的二阶空间频率。在中央凹旁位置，注意增强了对相对较高而非较低二阶空间频率的二阶对比敏感度。在本研究中我们调查了内源性注意——空间注意中更具自主性、由概念驱动的成分——是否会影响二阶对比敏感度，如果是，其效果是否与外源性注意的效果相似。为此，我们比较了外源性和内源性注意对高或低二阶空间频率的二阶方向定义纹理图案敏感度的影响。结果表明，与外源性注意一样，内源性注意在被关注位置增强二阶对比敏感度，在未被关注位置降低二阶对比敏感度。然而，外源性注意的效果是二阶空间频率内容的函数，而内源性注意对二阶对比敏感度的影响与二阶空间频率内容无关。这一发现支持了这样一种观点，即外源性和内源性注意都可以影响二阶对比敏感度，但内源性注意更具灵活性，在不同条件下都有利于表现。
