The neural bases of perceptual capacity limitations

描述（由申请人提供）：当我们看到拥挤或杂乱的场景时，人类视觉系统的有限处理能力是显而易见的。我们都经历过在人群中寻找朋友面孔的困难。尽管我们对要找的面孔很熟悉，但这种搜寻几乎总是缓慢而连续的；我们不能一次处理所有的面孔。在提出的一系列实验中，我们计划研究这种有限处理能力的神经基础。为什么我们一次只能处理有限数量的项目？选择性注意的偏见竞争理论为这种限制提供了一种解释。单细胞和功能磁共振成像研究都表明，当多个附近的刺激同时出现在视野中时，它们不是独立处理的，而是以相互抑制的方式相互作用的。此外，这种竞争已被证明在感受野（RF）水平上发生得最强烈。根据这一理论，处理能力的限制是刺激之间在感官水平上对神经表征的竞争的结果。然而，许多关于处理能力限制的行为文献认为处理能力限制是注意力能力有限的结果；也就是说，我们将注意力集中在多个项目上的能力受到限制，这一功能通常与额顶叶皮层有关。本实验的目的是利用功能磁共振成像研究视觉皮层中的神经竞争是否可以解释视觉系统有限的处理能力，或者有限的处理能力是否更好地反映在额顶叶皮层的活动和我们将注意力引导到多个位置的能力上。本文提出的实验将进一步加深我们对视觉过程和注意力的相互作用的理解，并对我们有限的处理能力的神经基础提供更深入的理解。了解限制我们在任何时候都能有效处理的视觉项目数量的神经机制，可能对治疗各种导致注意力能力下降的行为和大脑疾病有重要意义，包括注意力缺陷障碍、阿尔茨海默病和单侧忽视综合征。

DESCRIPTION (provided by applicant): The limited processing capacity of the human visual system is clear whenever we look at a crowded or cluttered scene. We have all experienced the difficulty in finding the face of a friend in a crowd. Despite our familiarity with the face we are looking for, such a search is almost always a slow and serial one; we cannot process all the faces at once. In the proposed set of experiments we plan to investigate the neural underpinnings of this limited processing capacity. Why is it that we can process only a limited number of items at a time? The biased competition theory of selective attention posits one explanation for this limitation. Both single-cell and fMRI studies have shown that when multiple nearby stimuli appear simultaneously in the visual field, they are not processed independently, but interact in a mutually suppressive way. Moreover, this competition has been shown to occur most strongly at the level of the receptive field (RF). Processing capacity limitations, by this theory then, are a consequence of competition among stimuli for neural representation at a sensory level. However, much of the behavioral literature on processing capacity limitations, have considered processing limitations to be a consequence of a limited attentional capacity; that is, a limit in our ability to direct attention towards multiple items, a function generally associated with the frontoparietal cortex. The objective of the proposed experiments is to use fMRI to investigate whether neural competition in the visual cortex can explain the limited processing capacity of the visual system or whether limited processing capacity is better reflected in the activity of the frontoparietal cortex and our ability to direct attention to multiple locations. The experiments proposed here should further our understanding of the interaction of visual processes and attention, as well as provide a deeper understanding of the neural basis of our limited processing capacity. Understanding the neural mechanism that constrain the number of visual items we can process effectively at any one time may have important implications in treating a variety of behavioral and brain disorders that result in diminished attentional capacity, including attention deficit disorder, Alzheimer's disease, and unilateral neglect syndrome.