School of Psychology, University of Aberdeen, Aberdeen AB24 3FX, United Kingdom, Department of Neurosciences, University of California, San Diego, La Jolla, California 92093, and Institute of Psychology, University of Leipzig, 04103 Leipzig, Germany.
J Neurosci. 2013 Nov 13;33(46):18200-7. doi: 10.1523/JNEUROSCI.1913-13.2013.
In many common situations such as driving an automobile it is advantageous to attend concurrently to events at different locations (e.g., the car in front, the pedestrian to the side). While spatial attention can be divided effectively between separate locations, studies investigating attention to nonspatial features have often reported a "global effect", whereby items having the attended feature may be preferentially processed throughout the entire visual field. These findings suggest that spatial and feature-based attention may at times act in direct opposition: spatially divided foci of attention cannot be truly independent if feature attention is spatially global and thereby affects all foci equally. In two experiments, human observers attended concurrently to one of two overlapping fields of dots of different colors presented in both the left and right visual fields. When the same color or two different colors were attended on the two sides, deviant targets were detected accurately, and visual-cortical potentials elicited by attended dots were enhanced. However, when the attended color on one side matched the ignored color on the opposite side, attentional modulation of cortical potentials was abolished. This loss of feature selectivity could be attributed to enhanced processing of unattended items that shared the color of the attended items in the opposite field. Thus, while it is possible to attend to two different colors at the same time, this ability is fundamentally constrained by spatially global feature enhancement in early visual-cortical areas, which is obligatory and persists even when it explicitly conflicts with task demands.
在许多常见的情况下，如驾驶汽车，同时关注不同位置的事件是有利的（例如，前面的汽车，旁边的行人）。虽然空间注意力可以有效地分配到不同的位置，但研究注意力对非空间特征的注意力通常会报告“全局效应”，即具有注意特征的项目可能会在整个视野中被优先处理。这些发现表明，空间和基于特征的注意力有时可能会直接对立：如果特征注意力是空间全局的，并且平等地影响所有焦点，那么空间上分散的注意力焦点就不能真正独立。在两项实验中，人类观察者同时关注左右视野中呈现的两个不同颜色的重叠点场之一。当两侧的注意力相同或两种不同的颜色时，偏离目标被准确地检测到，并且由注意点引起的视觉皮质电位增强。然而，当一侧的注意颜色与另一侧的忽略颜色相匹配时，皮质电位的注意力调节被取消。这种特征选择性的丧失可以归因于对未被注意的项目的处理增强，这些项目在对面的场中共享被注意项目的颜色。因此，虽然有可能同时关注两种不同的颜色，但这种能力受到早期视觉皮质区域中空间全局特征增强的根本限制，即使它与任务需求明确冲突，这种增强也是强制性的并且仍然存在。
