Testing sensory evidence against mnemonic templates.
Testing sensory evidence against mnemonic templates.
复制标题
测试针对助记符模板的感觉证据。
DOI：
10.7554/elife.09000
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发表时间：
2015-12-14
期刊：
影响因子：
7.7
通讯作者：
Stokes MG
中科院分区：
文献类型：
--
作者：
Myers NE;Rohenkohl G;Wyart V;Woolrich MW;Nobre AC;Stokes MG
大多数感知决策需要在当前输入和内部模板之间进行比较。经典的研究提出，模板编码在持续的感觉神经元的活动。然而，刺激编码本身是动态的，通过活动空间追踪复杂的轨迹。这个轨迹的哪一部分是预先激活的，以反映模板？在这里，我们记录了磁和脑电图在视觉目标检测任务，并使用模式分析解码模板，刺激和决策变量表示。我们的研究结果与持续预激活的主导模型背道而驰。相反，模板信息出现短暂刺激发作和迅速消退。刺激和模板编码之间的交叉概括（表明共享的神经表征）只发生了短暂的时间。我们的研究结果是兼容的建议，模板表示依赖于匹配过滤器，将输入转换为任务适当的输出。这个提议与感知决策阶段的符号差异反应一致，这可以通过一个简单的神经模型来解释。http://dx.doi.org/10.7554/eLife.09000.001想象一下，在一张杂乱的桌子上寻找你家的钥匙。你的眼睛扫描不同的项目，直到他们最终找到你正在寻找的钥匙。在过去的30年里，大脑如何代表你搜索的目标（在这个例子中是钥匙）的内部模板一直是神经科学中一个备受争议的话题。先前的研究表明，当我们寻找目标时，专门用于检测目标的神经元也会被预先激活，这意味着这些“模板”神经元在我们搜索的整个过程中都处于活跃状态。 当志愿者试图检测电脑屏幕上出现的特定形状时，研究人员使用一种名为脑磁图（MEG）的非侵入性技术记录了他们的大脑活动。大脑活动的模式可以被分析，以确定观察者心目中的模板，并跟踪它何时变得活跃。这表明，模板只有在目标可能出现的时候才会被激活，之后激活模式又迅速消退。 他还发现，在脑海中记住一个模板，与看到电脑屏幕上出现相同的形状时激活的神经元群在很大程度上是不同的。这与相同的细胞负责维持模板并感知其在我们周围的存在的想法相反。模板的短暂激活表明，模板可能主要是为了过滤新的感官证据来检测目标。这种机制可能是有利的，因为它降低了任务所需的神经活动量（从而降低了能量）。虽然这表明大脑搜索目标的方式更有效，但这些发现需要使用其他方法和任务设置来复制，以确认大脑是否通常以这种方式使用模板。DOI：http://dx.doi.org/10.7554/eLife.09000.002网站
Most perceptual decisions require comparisons between current input and an internal template. Classic studies propose that templates are encoded in sustained activity of sensory neurons. However, stimulus encoding is itself dynamic, tracing a complex trajectory through activity space. Which part of this trajectory is pre-activated to reflect the template? Here we recorded magneto- and electroencephalography during a visual target-detection task, and used pattern analyses to decode template, stimulus, and decision-variable representation. Our findings ran counter to the dominant model of sustained pre-activation. Instead, template information emerged transiently around stimulus onset and quickly subsided. Cross-generalization between stimulus and template coding, indicating a shared neural representation, occurred only briefly. Our results are compatible with the proposal that template representation relies on a matched filter, transforming input into task-appropriate output. This proposal was consistent with a signed difference response at the perceptual decision stage, which can be explained by a simple neural model. DOI: http://dx.doi.org/10.7554/eLife.09000.001 Imagine searching for your house keys on a cluttered desk. Your eyes scan different items until they eventually find the keys you are looking for. How the brain represents an internal template of the target of your search (the keys, in this example) has been a much-debated topic in neuroscience for the past 30 years. Previous research has indicated that neurons specialized for detecting the sought-after object when it is in view are also pre-activated when we are seeking it. This would mean that these ‘template’ neurons are active the entire time that we are searching. recorded brain activity from human volunteers using a non-invasive technique called magnetoencephalography (MEG) as they tried to detect when a particular shape appeared on a computer screen. The patterns of brain activity could be analyzed to identify the template that observers had in mind, and to trace when it became active. This revealed that the template was only activated around the time when a target was likely to appear, after which the activation pattern quickly subsided again. also found that holding a template in mind largely activated different groups of neurons to those activated when seeing the same shape appear on a computer screen. This is contrary to the idea that the same cells are responsible both for maintaining a template and for perceiving its presence in our surroundings. The brief activation of the template suggests that templates may come online mainly to filter new sensory evidence to detect targets. This mechanism could be advantageous because it lowers the amount of neural activity (and hence energy) needed for the task. Although this points to a more efficient way in which the brain searches for targets, these findings need to be replicated using other methods and task settings to confirm whether the brain generally uses templates in this way. DOI: http://dx.doi.org/10.7554/eLife.09000.002