Neuronal Mechanisms Mediating Visual Search

描述(申请人提供)：典型的视觉场景将包含许多不同的对象，其中很少有对象与手头的任务相关。因此，需要注意力机制来找到相关的物体并抑制干扰因素。对这些注意力机制的了解最终将有助于为有严重视觉障碍的人开发视觉假体，也将有助于开发治疗包括ADHD在内的影响注意力的大脑疾病的方法。这一提议的长期目标不仅是为了揭示注意力对大脑视觉处理的影响，还在于了解这些影响发生的神经机制。特别重要的是要了解注意机制在自然主义条件下是如何运作的，例如当我们根据物体的特征自由移动视线寻找物体时(例如，视觉搜索，或在人群中寻找一张脸)。我们的重点是视觉区域V4，这是皮层通路中的一个中间处理阶段，对物体识别非常重要。新的结果表明，偏向于行为相关刺激的注意偏差可能不仅涉及V4神经元平均放电频率的变化，还涉及V4活动的同步时序。第一个具体目标是检验关于V4区上层和下层在视觉搜索中对基于特征的注意的不同功能贡献的假设。下一个目标是确定放电率和神经同步性对参与视觉搜索的动物的行为表现的具体贡献。第三个目的是确定前额叶皮质在视觉搜索过程中对V4神经元反应和同步性的注意效应的贡献。这些目的将使我们更好地了解视觉皮质中注意的功能解剖，特定的生物注意机制对行为的贡献，以及自上而下反馈到视觉皮质的性质。研究计划的中心假设是，前额叶皮质的神经元在腹侧流视觉区域(如V4区)引起放电频率和神经同步性的变化，这些变化中介了在视觉搜索的自然条件下对相关对象的选择。这些假设测试了新的想法，但它们得到了初步数据的很好支持，而且我们有很好的条件来测试它们，因为我们已经有了多年的技术经验。

DESCRIPTION (provided by applicant): A typical visual scene will contain many different objects, few of which will be relevant to the task at hand. Thus, attentional mechanisms are needed to find relevant objects and suppress distracters. An understanding of these attentional mechanisms will ultimately help in developing a visual prosthesis for people with severe visual impairments, and will also help in developing treatments for people with brain disorders affecting attention, including ADHD. The long term goal of this proposal is to not only uncover attentional influences on visual processing in the brain, but also to understand the neuronal mechanisms by which these effects occur. It is particularly important to understand how the attentional mechanism operates under naturalistic conditions, such as when we freely move our gaze to find objects based on their features (e.g. visual search, or finding a "face in a crowd"). Our focus is on visual area V4, which is an intermediate processing stage in the cortical pathway important for object recognition. New results suggest that the attentional bias in favor of behaviorally relevant stimuli may involve not only changes in the average firing rate of V4 neurons, but also the synchronous timing of V4 activity. The first specific aim is to test hypotheses about the different functional contributions of the upper and lower layers in area V4 to feature-based attention in visual search. The next aim is to establish the specific contributions of firing rates and neural synchrony to the behavioral performance of animals engaged in visual search. The third aim is to determine the contribution of prefrontal cortex to the attentional effects on V4 neuronal responses and synchrony during visual search. These aims will give us a better understanding of the functional anatomy of attention in the visual cortex, the contributions of specific biological mechanisms of attention to behavior, and the nature of top-down feedback to the visual cortex. The central hypothesis of the research program is that neurons in prefrontal cortex induce changes in both firing rates and neural synchrony in ventral stream visual areas such as area V4, and that these changes mediate the selection of relevant objects under naturalistic conditions of visual search. These hypotheses test novel ideas, but they are well supported by preliminary data, and we are well-positioned to test them since we have had many years of experience with the techniques.