Task context impacts visual object processing differentially across the cortex
Task context impacts visual object processing differentially across the cortex
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DOI：
10.1073/pnas.1312567111
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发表时间：
2014-03-11
影响因子：
11.1
通讯作者：
Baker, Chris I.
中科院分区：
文献类型：
--
作者：
Harel, Assaf;Kravitz, Dwight J.;Baker, Chris I.
知觉反映了“自下而上”(感官驱动)和“自上而下”(内部产生)信号的整合。虽然视觉加工的模型经常强调前馈分层加工的中心作用，但对自上而下信号对复杂视觉表征的影响知之甚少。在这里，我们调查了观察者的目标是否以及如何调节大脑皮层中的物体处理。我们考察了一组不同的物体在六个不同的任务下引起的反应，重点是物理(例如，颜色)或概念属性(例如，人造)。重要的是，在所有任务中都呈现了相同的刺激，这使得我们能够研究任务如何影响相同视觉输入的神经表征。我们发现，这项任务对大脑皮层的物体处理有广泛而不同的影响。首先，我们在前额叶和额叶腹侧皮质发现了任务依赖性表征。具体地说，虽然可以从任务内的多体素响应中解码对象身份，但跨任务的解码显著减少。相比之下，早期的视皮层在任务内和任务之间显示出等同的解码，表明任务无关的表征。第二，任务信息从客体加工的最早阶段起就是无处不在的。然而，尽管腹侧颞叶、前额叶和顶叶皮质的反应能够对任务类型(物理/概念)和特定任务(如颜色)进行解码，但早期的视觉皮质对任务类型不敏感，只能用于解码个别物理任务。因此，对象处理在很大程度上受观察者的行为目标的影响，突出了自上而下的信号如何约束和通知视觉表示的形成。
Perception reflects an integration of "bottom-up" (sensory-driven) and "top-down" (internally generated) signals. Although models of visual processing often emphasize the central role of feed-forward hierarchical processing, less is known about the impact of top-down signals on complex visual representations. Here, we investigated whether and how the observer's goals modulate object processing across the cortex. We examined responses elicited by a diverse set of objects under six distinct tasks, focusing on either physical (e.g., color) or conceptual properties (e.g., man-made). Critically, the same stimuli were presented in all tasks, allowing us to investigate how task impacts the neural representations of identical visual input. We found that task has an extensive and differential impact on object processing across the cortex. First, we found task-dependent representations in the ventral temporal and prefrontal cortex. In particular, although object identity could be decoded from the multivoxel response within task, there was a significant reduction in decoding across tasks. In contrast, the early visual cortex evidenced equivalent decoding within and across tasks, indicating task-independent representations. Second, task information was pervasive and present from the earliest stages of object processing. However, although the responses of the ventral temporal, prefrontal, and parietal cortex enabled decoding of both the type of task (physical/conceptual) and the specific task (e.g., color), the early visual cortex was not sensitive to type of task and could only be used to decode individual physical tasks. Thus, object processing is highly influenced by the behavioral goal of the observer, highlighting how top-down signals constrain and inform the formation of visual representations.