Modulation of visual cortex by attention and uncertainty

描述(申请人提供)：拟议的实验将调查先前的知识和期望如何影响视觉注意的控制和视觉输入的处理。具体地说，假设基底前脑胆碱能核团的活动是为了表明受试者对即将发生的事件的不确定性水平。在低不确定性条件下，在分析早期大脑皮层区域的视觉信息时，应强调代表被试期望的自上而下的注意相关信号。另一方面，当不确定性很高时，这些自上而下的输入中几乎没有有用的信息，应该促进自下而上的刺激相关信号。功能磁共振成像(FMRI)技术将被用来测量受试者在低不确定性或高不确定性条件下做出视觉判断时不同脑区的大脑活动。这些研究还将确定顶叶和额叶的候选区域，这些区域负责调节对空间中某个位置的注意，而不是对视觉对象特定特征的注意。最后，自下而上的感觉输入和它们被自上而下的注意信号调制之间的相互作用将在早期的视觉皮质中被测量，并与心理物理任务的表现相关联。除了提供有关注意力在大脑中如何表现以及它如何影响视觉刺激处理的信息外，本实验还应该阐明从基底前脑到大脑皮层的胆碱能投射的功能。由于这种投射在阿尔茨海默病中被认为是选择性受损的，了解它在健康大脑中的功能可能有助于理解这种疾病的病因，并有助于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.