When does perceptual organization happen?

每当我们的眼皮张开时，一个图像就会投射到眼球后面的视网膜上。但当我们处于无意识状态时，这种情况就会发生。要想看到任何东西，视觉大脑必须组织和解释视网膜图像。在其他方面，视觉大脑必须弄清楚哪些特征属于同一个物体，表面是如何深度排列的，哪些表面特征是由照明引起的，哪些是由色素沉着引起的。大脑的视觉部分充满了调节知觉组织的机制。我们的项目将测试视觉大脑何时费力组织和解释视网膜图像。在一个极端情况下，我们的知觉组织系统可能在我们醒着的时候处于“红色警戒”状态。也许完整的知觉组织总是发生的，无论它是不是与任务相关？在另一个极端，感性的组织系统可能经常默认为“待命模式”。也许只有在必要的时候才会进行知觉组织，而视网膜图像往往不被解读？此外，知觉组织可能对精神状态的变化很健壮或敏感。例如，急性或慢性饮酒可能会扰乱知觉组织机制。视觉对称性是回答这些问题的完美刺激。首先，我们可以精确地定义和控制抽象对称模式的形式属性。第二，对称模式产生事件相关电位(ERP)，称为持续性后负波(SPN)。这种神经信号已经得到了很好的表征，并且可以用头皮电极廉价地进行测量。SPN是由已知的大脑区域(V4和LOC)产生的，它可以作为知觉组织的生物标志。如果头皮上有SPN，那么视觉大脑中就发生了知觉组织。工作包1将发现产生SPN的条件：例如，当参与者关注颜色或声音而不是对称性时，SPN可能会减少。工作包2将使用功能磁共振成像(FMRI)和先进的多体素模式分析(MVPA)来评估参与者在注意对称、颜色或声音时视觉对称码的变化。这可以告诉我们，当注意力转移到其他地方时，视觉皮质中的对称性表征是如何恶化的。接下来，WP3将使用经颅磁刺激(TMS)来评估不同大脑区域在自动知觉组织中的因果必要性。最后，我们的工作包4有一个应用维度。我们想要发现酒精是如何改变知觉组织的。尽管酒精是英国最广泛使用的一种被滥用的娱乐药物，但人们对酒精对知觉组织的急性和慢性影响知之甚少。我们将测试酒精降低左右视觉半球之间神经交流速度的理论。我们预测，对垂直对称性的SPN反应将选择性地被轻度醉酒延迟，并且在目前清醒的重度饮酒者中。这有可能有助于基于证据的饮酒意识运动，但只有在WP1-3中建立基础研究才有可能。最终，我们将开发新的研究工具，任何人都可以下载并使用它来测量酒精诱导的大脑变化。这一点很重要，因为在这一领域从基础研究到应用研究的转化往往会受到实际障碍的阻碍。我们这个项目的研究团队是经过精心挑选的。马金、贝尔塔米尼和兰彭是对称性感知、脑电记录和分析方面的专家。莫兰德教授拥有丰富的使用功能磁共振成像绘制视觉皮质图的经验。西尔万托是用TMS研究对称性知觉的专家。琼斯是利物浦领先的酒精/脑电研究人员，他非常有能力推动该项目的应用领域。

Whenever our eyelids are open, an image is projected onto the retina at the back of the eyeball. But this can happen when we are unconscious. To see anything, the visual brain must organize and interpret the retinal image. Among other things, the visual brain must work out what features belong to the same object, how surfaces are arranged in depth, which surface features are caused by illumination and which by pigmentation. The visual parts of the brain are full of mechanisms which mediate perceptual organization. Our project will test WHEN the visual brain goes to the trouble of organizing and interpreting the retinal image. At one extreme, our perceptual organization systems could be 'on red alert' whenever we are awake. Perhaps complete perceptual organization always happens, whether it is task-relevant or not? At the other extreme, perceptual organization systems might frequently default to 'stand by mode'. Perhaps perceptual organization is only undertaken when necessary, and the retinal image is often left uninterpreted? Furthermore, perceptual organization might be robust or sensitive to changes in mental state. For instance, perceptual organization mechanisms might be disrupted by acute or chronic to alcohol consumption.Visual symmetry is the perfect stimulus to answer these questions. First, we can precisely define and control the formal properties of abstract symmetrical patterns. Second, symmetrical patterns generate an Event Related Potential (ERP) called the Sustained Posterior Negativity (SPN). This neural signal has been well characterized, and it can be cheaply measured with scalp electrodes. The SPN is generated by known brain regions (V4 and LOC), and it can be used as a bio-marker of perceptual organization. If there is an SPN on the scalp, then perceptual organization has happened in the visual brain. Work package 1 will the discover the conditions for SPN generation: For instance, the SPN might be reduced when participants are attending to color or sound rather than symmetry. Work package 2 will use functional Magnetic Resonance Imaging (fMRI) and advanced multi-voxel pattern analysis (MVPA) to assess changes to the visual symmetry code when participants attend to symmetry, color or sound. This can tell us how the symmetry representations in the visual cortex deteriorate when attention is directed elsewhere. Next, WP3, will use Transcranial Magnetic Stimulation (TMS) to assess the causal necessity of the different brain areas in automatic perceptual organization. Finally our Work package 4 has an applied dimension. We want to discover how perceptual organization is altered by alcohol. Although alcohol is the most widely used an abused recreational drug in the UK, little is known about acute and chronic effects on perceptual organization. We will test the theory that alcohol reduces the speed of neural communication between the left and right visual hemispheres. We predict that the SPN response to vertical symmetry will be selectively delayed by mild intoxication, and in currently sober heavy drinkers. This has the potential to contribute to evidence based drink awareness campaigns, but it is only possible by building in the basic research in WP1-3. Ultimately, we will develop new research tool which anybody can download and use to measure alcohol-induced brain changes. This is important because the translation from basic to applied research in this area is often blocked by practical obstacles. Our research team for this project is carefully chosen. Makin, Bertamini and Rampone are experts in symmetry perception, EEG recording and analysis. Prof Morland has extensive experience using fMRI to map the visual cortex. Silvanto is an expert on studying symmetry perception with TMS. Jones is a leading alcohol/EEG researcher at Liverpool, who is well placed to push the applied dimension of the project.