Exponent, Inc., Los Angeles, CA, USA.
Neuropsychologia. 2011 May;49(6):1527-36. doi: 10.1016/j.neuropsychologia.2011.01.040. Epub 2011 Feb 15.
The encoding of information into visual working memory (VWM) is not only a prerequisite step for efficient working memory, it is also considered to limit our ability to attend to, and be consciously aware of, task-relevant events. Despite its important role in visual cognition, the neural mechanisms underlying visual working memory encoding have not yet been specifically dissociated from those involved in perception and/or VWM maintenance. To isolate the brain substrates supporting VWM encoding, here we sought to identify, with time-resolved fMRI, brain regions whose temporal profile of activation tracked the time course of VWM encoding. We applied this approach to two different stimulus categories - colors and faces - that dramatically differ in their encoding time. While several cortical and subcortical regions were activated during the VWM encoding period, one of these regions in the lateral prefrontal cortex - the inferior frontal junction - showed a temporal activation profile associated with the duration of encoding and that could not be accounted for by either perceptual or general attentional effects. Moreover, this region corresponds to the prefrontal area previously implicated in 'attentional blink' paradigms demonstrating attentional limits to conscious perception. These results not only suggest that the inferior frontal junction is involved in VWM encoding, they also provide neural support for theories positing that VWM encoding is a rate-limiting process underlying our attentional limits to visual awareness.
信息在视觉工作记忆（VWM）中的编码不仅是高效工作记忆的先决条件步骤，它也被认为限制了我们注意和有意识地意识到与任务相关的事件的能力。尽管它在视觉认知中具有重要作用，但视觉工作记忆编码背后的神经机制尚未与感知和/或 VWM 维持所涉及的机制明确区分开来。为了分离支持 VWM 编码的大脑基质，我们在这里试图使用时间分辨 fMRI 来识别，其激活的时间过程与 VWM 编码的时间过程相吻合的大脑区域。我们将这种方法应用于两种不同的刺激类别 - 颜色和面孔 - 它们在编码时间上有很大的不同。虽然在 VWM 编码期间激活了几个皮质和皮质下区域，但其中一个在外侧前额叶皮层中的区域 - 下额前联合 - 显示出与编码持续时间相关的时间激活模式，而不能用感知或一般注意力效应来解释。此外，这个区域与先前在证明对视觉意识的注意力限制的“注意眨眼”范式中涉及的前额区域相对应。这些结果不仅表明下额前联合参与了 VWM 编码，而且还为以下理论提供了神经支持，即 VWM 编码是我们对视觉意识的注意力限制的一个限速过程。
