Poltoratski Sonia, Ling Sam, McCormack Devin, Tong Frank
Vanderbilt Vision Research Center, Psychology Department, Vanderbilt University, Nashville, Tennessee; and
Department of Psychological & Brain Sciences, Center for Computational Neuroscience and Neural Technology, Boston University, Boston, Massachusetts.
J Neurophysiol. 2017 Jul 1;118(1):564-573. doi: 10.1152/jn.00924.2016. Epub 2017 Apr 5.
The visual system employs a sophisticated balance of attentional mechanisms: salient stimuli are prioritized for visual processing, yet observers can also ignore such stimuli when their goals require directing attention elsewhere. A powerful determinant of visual salience is local feature contrast: if a local region differs from its immediate surround along one or more feature dimensions, it will appear more salient. We used high-resolution functional MRI (fMRI) at 7T to characterize the modulatory effects of bottom-up salience and top-down voluntary attention within multiple sites along the early visual pathway, including visual areas V1-V4 and the lateral geniculate nucleus (LGN). Observers viewed arrays of spatially distributed gratings, where one of the gratings immediately to the left or right of fixation differed from all other items in orientation or motion direction, making it salient. To investigate the effects of directed attention, observers were cued to attend to the grating to the left or right of fixation, which was either salient or nonsalient. Results revealed reliable additive effects of top-down attention and stimulus-driven salience throughout visual areas V1-hV4. In comparison, the LGN exhibited significant attentional enhancement but was not reliably modulated by orientation- or motion-defined salience. Our findings indicate that top-down effects of spatial attention can influence visual processing at the earliest possible site along the visual pathway, including the LGN, whereas the processing of orientation- and motion-driven salience primarily involves feature-selective interactions that take place in early cortical visual areas. While spatial attention allows for specific, goal-driven enhancement of stimuli, salient items outside of the current focus of attention must also be prioritized. We used 7T fMRI to compare salience and spatial attentional enhancement along the early visual hierarchy. We report additive effects of attention and bottom-up salience in early visual areas, suggesting that salience enhancement is not contingent on the observer's attentional state.
显著刺激在视觉处理中被优先考虑，但当观察者的目标需要将注意力转向其他地方时，他们也可以忽略此类刺激。视觉显著性的一个重要决定因素是局部特征对比度：如果一个局部区域在一个或多个特征维度上与其紧邻的周围区域不同，它就会显得更显著。我们使用7T高分辨率功能磁共振成像（fMRI）来表征早期视觉通路多个部位（包括视觉区域V1-V4和外侧膝状体核（LGN））自下而上的显著性和自上而下的自愿性注意力的调节作用。观察者观看空间分布的光栅阵列，其中位于注视点左侧或右侧紧邻的一个光栅在方向或运动方向上与所有其他项目不同，从而使其显得显著。为了研究定向注意力的影响，提示观察者关注注视点左侧或右侧的光栅，该光栅要么显著要么不显著。结果显示，在整个视觉区域V1-hV4中，自上而下的注意力和刺激驱动的显著性具有可靠的叠加效应。相比之下，LGN表现出显著的注意力增强，但并未受到方向或运动定义的显著性的可靠调节。我们的研究结果表明，空间注意力的自上而下效应可以在视觉通路的最早部位（包括LGN）影响视觉处理，而方向和运动驱动的显著性处理主要涉及在早期皮质视觉区域发生的特征选择性相互作用。虽然空间注意力允许对刺激进行特定的、目标驱动的增强，但当前注意力焦点之外的显著项目也必须被优先考虑。我们使用7T fMRI来比较早期视觉层级中的显著性和空间注意力增强。我们报告了早期视觉区域中注意力和自下而上显著性的叠加效应，这表明显著性增强并不取决于观察者的注意力状态。
