Yi Do-Joon, Kelley Todd A, Marois René, Chun Marvin M
Department of Psychology, Yale University, PO Box 208205, New Haven, CT 06520-8205, USA.
Brain Res. 2006 Mar 29;1080(1):53-62. doi: 10.1016/j.brainres.2006.01.090. Epub 2006 Feb 28.
Repeating a stimulus generally leads to a decreased response in neural activity compared to that for novel items. This neural attenuation provides a marker for stimulus-specific perceptual encoding and memory that can be detected using functional magnetic resonance imaging (fMRI). Although previously assumed to occur automatically whenever a stimulus is repeated, recent studies have begun to show that the repetition attenuation effect is task-specific and modulated by attention. Here, we demonstrate that attention is crucial for obtaining neural attenuation even after extensive stimulus repetitions. Furthermore, the effect of attention on attenuation is anatomically dissociable for stimuli that have relatively segregated neural representations in high-level perceptual cortex. To manipulate attention, we used overlapping scene and face images, and asked subjects to attend to either category. In a scene-sensitive cortical region known as the parahippocampal place area (PPA), significant attenuation in the fMRI BOLD signal was observed for the attended repeated scenes (relative to attended novel scenes), while no attenuation was observed for ignored repeated scenes or attended repeated faces against their respective novel image baselines. Conversely, in the face-sensitive region known as the fusiform face area (FFA), significant attenuation was observed for attended repeated faces, but not for ignored repeated faces or attended repeated scenes. An additional control experiment ruled out alternative explanations based on global signal level reductions due to inattention. Thus, attention actively governed when neuronal activity was attenuated to repeated perceptual input, and such attenuation was specific to the cortical regions that actively represent the attended category of stimuli.
与新异刺激相比，重复刺激通常会导致神经活动反应降低。这种神经衰减为刺激特异性感知编码和记忆提供了一个标记，可通过功能磁共振成像（fMRI）检测到。尽管之前认为只要刺激重复就会自动出现这种情况，但最近的研究开始表明，重复衰减效应是任务特异性的，并受注意力调节。在这里，我们证明即使在大量刺激重复之后，注意力对于获得神经衰减也是至关重要的。此外，对于在高级感知皮层中具有相对分离的神经表征的刺激，注意力对衰减的影响在解剖学上是可分离的。为了操纵注意力，我们使用了重叠的场景和面部图像，并要求受试者关注其中任何一个类别。在一个被称为海马旁回位置区（PPA）的对场景敏感的皮层区域，相对于关注的新异场景，对关注的重复场景观察到fMRI血氧水平依赖（BOLD）信号的显著衰减，而对于被忽视的重复场景或相对于各自新异图像基线的关注的重复面部则未观察到衰减。相反，在一个被称为梭状回面孔区（FFA）的对面部敏感的区域，对关注的重复面部观察到显著衰减，但对被忽视的重复面部或关注的重复场景则未观察到衰减。一项额外的对照实验排除了基于注意力不集中导致的全局信号水平降低的其他解释。因此，注意力积极地控制着神经元活动何时因重复的感知输入而衰减，并且这种衰减特定于积极表征所关注刺激类别的皮层区域。
