Müller Notger G, Donner Tobias H, Bartelt Oliver A, Brandt Stephan A, Villringer Arno, Kleinschmidt Andreas
Cognitive Neurology Unit, Department of Neurology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
Neuroimage. 2003 Nov;20(3):1578-90. doi: 10.1016/s1053-8119(03)00416-6.
Visual conjunction search is proposed to be a multicomponent process which involves scaling and successive shifts of attention in space as well as object identification. Here, we first mapped brain areas sustaining the proposed attentional subprocesses and then tested whether their activity was modulated by search load, i.e., the number of shifts, as predicted by serial search models. Search load was manipulated indirectly by precueing a varying number of locations at which relevant objects were shown. Multiple subregions within the intraparietal sulcus (IPS) and the prefrontal cortex were activated after cueing. Activity in the right posterior IPS was modulated by the distance of attention shifts and in the left posterior IPS by "zooming out" to cover a large region of the visual field. More anterior subregions of the left IPS responded to object identification irrespective of the need for serial scanning. Corresponding regions in the right IPS were modulated parametrically with respect to search load, along with the right temporoparietal junction. These results support a functional segregation of subregions of the IPS. The posterior regions participate in large-scale shifts and scaling of the attentional focus and the anterior regions in object identification and rapid serial shifts during search. The sustained activation in the frontal eye fields after cueing suggests a role in maintaining attention in the periphery. Together with the findings in early visual areas from this experiment (Müller et al., 2003) the current observations are best accounted for by hybrid models of visual conjunction search, where parallel processing in visual and temporoparietal regions and serial scanning controlled by the right IPS cooperate.
视觉联合搜索被认为是一个多成分过程，它涉及注意力在空间中的缩放和连续转移以及物体识别。在这里，我们首先绘制了支持所提出的注意力子过程的脑区，然后测试它们的活动是否如串行搜索模型所预测的那样受到搜索负荷的调节，即转移的数量。通过预先提示显示相关物体的不同数量的位置来间接操纵搜索负荷。提示后，顶内沟（IPS）和前额叶皮层内的多个子区域被激活。右后IPS的活动受注意力转移距离的调节，左后IPS的活动受“放大”以覆盖视野的大区域的调节。无论是否需要串行扫描，左IPS的更靠前的子区域对物体识别有反应。右IPS的相应区域以及右颞顶联合区随搜索负荷进行参数调节。这些结果支持IPS子区域的功能分离。后部区域参与注意力焦点的大规模转移和缩放，前部区域参与搜索期间的物体识别和快速串行转移。提示后额眼区的持续激活表明其在维持周边注意力方面的作用。结合本实验早期视觉区域的发现（Müller等人，2003年），当前的观察结果最好由视觉联合搜索的混合模型来解释，其中视觉和颞顶区域的并行处理以及由右IPS控制的串行扫描相互协作。
