Hughes David H, Barnas Adam J, Greenberg Adam S
Joint Department of Biomedical Engineering, Medical College of Wisconsin and Marquette University, Milwaukee, Wisconsin, United States.
Department of Psychology, University of Florida, Gainesville, Florida, United States.
J Neurophysiol. 2025 Aug 1;134(2):504-516. doi: 10.1152/jn.00554.2024. Epub 2025 Jul 1.
Object-based attention prioritizes the processing of information appearing within a selected object. We previously showed an object-based shift direction anisotropy (SDA) whereby horizontal shifts are more efficient than vertical shifts (Barnas AJ, Greenberg AS. 78: 1985-1997, 2016; Barnas AJ, Greenberg AS. 27: 768-791, 2019), an effect modulated by the visual field meridians (Barnas AJ, Greenberg AS. 77: 2516-2532, 2024). Our present aim was to understand how the functional brain mechanisms of attention give rise to the SDA. We hypothesized that the SDA arises from attentional resources being partitioned differently by horizontal and vertical meridians. To test this, we used fMRI of the visual cortex while subjects shifted attention horizontally and vertically within a single, L-shaped object. An SDA was observed when targets crossed the visual field meridians, and the object vertex was positioned in the upper-left corner. However, no SDA was observed when the object vertex was positioned in the lower-right corner. Cue-related activations revealed that attention spreads throughout the vertical component of each object (even to locations where the target never appeared). In addition, the vertical meridian seemed to impede the spread of attention for the upper-left object's horizontal component. However, for the lower-right object, the horizontal component showed a similar attentional modulation to its vertical component, commensurate with behavioral performance in response to that object. These results suggest the efficiency of horizontal shifts crossing the vertical meridian is enhanced by the support of attentional resources from both hemispheres. As such, we offer a refinement of how the visual field meridians may influence the spread of object-based attention via an anisotropic attention gradient. Our previous behavioral work suggests that inconsistent object-based attention effects (measured as the same-object advantage) arise from differences in shift direction efficiency (a shift direction anisotropy) across the visual field meridians, such that shifts are faster horizontally than vertically. Using fMRI, we present neurobiological evidence that the meridians may cause an unequal allocation of object-based attentional resources. These results necessitate updating theories of object-based attentional selection to account for the effects of visual field meridians.
基于物体的注意力会优先处理出现在选定物体内的信息。我们之前展示了一种基于物体的移位方向各向异性（SDA），即水平移位比垂直移位更有效（Barnas AJ, Greenberg AS. 78: 1985 - 1997, 2016; Barnas AJ, Greenberg AS. 27: 768 - 791, 2019），这种效应受视野子午线调节（Barnas AJ, Greenberg AS. 77: 2516 - 2532, 2024）。我们目前的目标是了解注意力的功能性脑机制如何产生SDA。我们假设SDA源于水平和垂直子午线对注意力资源的不同分配。为了验证这一点，我们在受试者在单个L形物体内水平和垂直转移注意力时，对视觉皮层进行功能磁共振成像（fMRI）。当目标穿过视野子午线且物体顶点位于左上角时，观察到了SDA。然而，当物体顶点位于右下角时，未观察到SDA。与线索相关的激活显示，注意力会扩散到每个物体的垂直部分（甚至到目标从未出现过的位置）。此外，垂直子午线似乎会阻碍左上角物体水平部分的注意力扩散。然而，对于右下角的物体，水平部分显示出与其垂直部分相似的注意力调制，这与对该物体的行为表现相符。这些结果表明，跨越垂直子午线的水平移位效率因来自两个半球的注意力资源支持而提高。因此，我们对视野子午线如何通过各向异性注意力梯度影响基于物体的注意力扩散提出了一种改进。我们之前的行为学研究表明，不一致的基于物体的注意力效应（以同物体优势衡量）源于跨视野子午线的移位方向效率差异（移位方向各向异性），使得水平移位比垂直移位更快。通过功能磁共振成像，我们提供了神经生物学证据，表明子午线可能导致基于物体的注意力资源分配不均。这些结果需要更新基于物体的注意力选择理论，以考虑视野子午线的影响。
