Appelbaum Lawrence G, Norcia Anthony M
Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA.
J Vis. 2009 Oct 19;9(11):18.1-12. doi: 10.1167/9.11.18.
Here we use the steady-state visual evoked potential (SSVEP) to study attentive versus non-attentive processing of simple texture-defined shapes. By "tagging" the figure and background regions with different temporal frequencies, the method isolates response components associated with the figure region, the background region, and with non-linear spatio-temporal interactions between regions. Each of these response classes has a distinct scalp topography that is preserved under differing attentional task demands. In one task, attention was directed to discrimination of shape changes in the figure region. In the other task, a difficult letter discrimination was used to divert attentive processing resources away from the texture-defined form. Larger task-dependent effects were observed for figure responses and for the figure/background interaction than for the background responses. The figure region responses were delayed in occipital areas in the shape versus letter task conditions, while the region interactions were enhanced, especially in frontal areas. While a basic differentiation of figure from background processing occurred independent of task, attentive processing of elementary shapes recruited later occipital activity for figure processing and sustained non-linear figure/background interaction in frontal areas. Collectively, these results indicate that basic aspects of scene segmentation proceed pre-attentively, but that directed attention to the object shape engages a widely distributed network of brain areas including frontal and occipital regions.
在此，我们使用稳态视觉诱发电位（SSVEP）来研究对简单纹理定义形状的专注与非专注加工。通过用不同的时间频率“标记”图形和背景区域，该方法分离出与图形区域、背景区域以及区域间非线性时空相互作用相关的反应成分。这些反应类别中的每一个都有独特的头皮地形图，且在不同的注意力任务需求下得以保留。在一项任务中，注意力被引导至辨别图形区域中的形状变化。在另一项任务中，通过一项困难的字母辨别任务来转移专注加工资源，使其远离纹理定义的形状。与背景反应相比，在图形反应和图形/背景相互作用方面观察到了更大的任务依赖效应。在形状与字母任务条件下，图形区域反应在枕叶区域延迟，而区域间相互作用增强，尤其是在额叶区域。虽然图形与背景加工的基本区分在任务之外就已发生，但对基本形状的专注加工会在枕叶后期招募用于图形加工的活动，并在额叶区域维持非线性的图形/背景相互作用。总体而言，这些结果表明，场景分割的基本方面在注意力之前就已进行，但对物体形状的定向注意力会涉及包括额叶和枕叶区域在内的广泛分布的脑区网络。
