Modulation of visual cortex by attention and uncertainty

描述（由申请人提供）：拟进行的实验将探讨先验知识和期望如何影响视觉注意的控制和视觉输入的处理。具体来说，假设基底前脑胆碱能核的活动表明受试者对即将发生的事件的不确定程度。在低不确定性条件下，对大脑皮层早期区域视觉信息的分析应强调自上而下的、代表被试期望的注意相关信号。另一方面，当不确定性较高时，这些自上而下的输入中有用的信息很少，应促进自下而上的刺激相关信号。功能磁共振成像技术（fMRI）将被用于测量受试者在低或高不确定性条件下进行视觉判断时不同脑区的脑活动。这些研究还将确定顶叶和额叶中的候选区域，这些区域调节对空间中某个位置的注意力，而不是对视觉物体特定特征的注意力。最后，自下而上的感觉输入和自上而下的注意信号之间的相互作用将在早期视觉皮层被测量，并与心理物理任务的表现相关。除了提供关于注意力如何在大脑中表现以及它如何影响视觉刺激处理的信息外，本实验还应阐明从基底前脑到大脑皮层的胆碱能投射的功能。由于这一突起被认为在阿尔茨海默病中选择性受损，因此了解其在健康大脑中的功能可能有助于了解该病的病因和开发适当的治疗方法。

DESCRIPTION (provided by applicant): The proposed experiments will investigate how prior knowledge and expectations affect the control of visual attention and processing of visual inputs. Specifically, activity in the cholinergic nuclei of the basal forebrain is hypothesized to signal the level of uncertainty subjects have about upcoming events. Under conditions of low uncertainty, top-down attention-related signals representing subjects' expectations should be emphasized in the analysis of visual information in early cortical areas. On the other hand, when uncertainty is high, there is little useful information in these top-down inputs, and bottom-up stimulus-related signals should be facilitated. The technique of functional magnetic resonance imaging (fMRI) will be employed to measure brain activity in different brain areas while subjects are making visual judgments under conditions of low or high uncertainty. These studies will also identify candidate areas in the parietal and frontal lobes that mediate attention to a location in space versus attention to specific features of visual objects. Finally, the interactions between bottom-up sensory inputs and their modulation by top-down attentional signals will be measured in early visual cortex and correlated with performance on psychophysical tasks. In addition to providing information about how attention is represented in the brain and how it affects processing of visual stimuli, the present experiments should also shed light on the function of the cholinergic projection from the basal forebrain to the cerebral cortex. As this projection is thought to be selectively impaired in Alzheimer's disease, knowledge concerning its function in the healthy brain may be useful for understanding the etiology of this disease and for development of appropriate therapies.