Interactions between LIP and V4 during top-down visual attention

描述（由申请人提供）：当人们面对日常拥挤的视觉场景时，需要注意机制将视觉处理限制在当前与行为相关的物体上。一般认为，感觉信息向更高层次大脑过程的过滤是由后顶叶皮质（PPC）等区域自上而下的控制信号调节的。本研究的目的是揭示PPC的一个分支——侧顶叶内区（LIP）——自上而下注意力的机制。我们将采用系统水平的神经生理学方法来研究LIP与早期腹侧流视觉区V4之间自上而下的相互作用。我们的第一个目标是利用LIP和V4的成对同时记录来量化每个区域和跨区域内的放电率和局部场电位（LFP）测量的注意调制效应的时间过程和幅度。关于LIP在V4中驱动注意调节中的作用，包括两个区域之间功能耦合的作用，我们将测试几个假设。第二个目标将直接评估在选择性视觉注意期间LIP对V4的因果影响，使用新的光遗传学技术来沉默/激活LIP中的兴奋性神经元。首先，LIP将暂时沉默，以消除自上而下的注意反馈，直接抑制V4神经活动的注意调节，损害行为表现。其次，激活LIP，直接将自上而下的注意反馈偏向于特定的刺激位置，同时测试由此产生的对相关V4神经元、跨区域同步和行为的影响。了解LIP中自上而下的注意机制的神经基础将有助于开发一种视觉假体来帮助严重视力障碍的人。此外，利用光遗传学以毫秒精度操纵视觉系统中的细胞的能力有望显著提高用于视觉神经假体的下一代脑刺激器的能力。

DESCRIPTION (provided by applicant): When people are confronted by an everyday, crowded visual scene, attentional mechanisms are needed to restrict visual processing to objects that are currently relevant to behavior. It is generally believed that the filtering of sensory information into higher level brain processes is regulated by top-down control signals in areas such as posterior parietal cortex (PPC). The goal of this proposal is to uncover the mechanisms of top- down attention employed by a subdivision of PPC, the lateral intraparietal area (LIP). A systems level neurophysiology approach will be taken to investigate the top-down interactions between LIP and an earlier ventral stream visual area, V4. Our first aim will utilize paired, simultaneous recordings in LIP and V4 to quantify the timecourse and magnitude of attentional modulation effects measured in the firing rate and local field potential (LFP) within each area and across areas. Several hypotheses will be tested concerning LIP's role in driving attentional modulation in V4, including the role of functional coupling between the two areas. The second aim will directly assess LIP's causal influence on V4 during selective visual attention using novel optogenetic techniques to silence/activate excitatory neurons in LIP. First, LIP will be momentarily silenced to remove top-down attentional feedback to V4 from LIP, directly suppressing attentional modulation of neural activity in V4 and impairing behavioral performance. Second, LIP will be activated so as to directly bias top- down attentional feedback toward a particular stimulus location while testing the resultant effects on associated V4 neurons, cross-area synchrony and behavior. An understanding of the neural basis of top-down attentional mechanisms in LIP will aid in developing a visual prosthesis to assist people with severe visual impairments. Furthermore, the ability to manipulate cells in the visual system at millisecond precision using optogenetics promises to significantly advance the capabilities of next-generation brain stimulators used in visual neural prostheses. PUBLIC HEALTH RELEVANCE: We expect that the successful implementation of this project will yield new insights into the mechanisms of top- down control of attention that will improve our understanding of central nervous system function in order to optimize the perceptual processing capabilities of people with low vision or blindness. Moreover, the use of novel optogenetic tools to probe attentional circuits by manipulating cells with millisecond precision will aid in the development of advanced neuro-stimulation approaches for visual prosthetics.