Bernstein Center for Computational Neuroscience, Charité Universitätsmedizin, Berlin, Germany.
Neuroimage. 2012 Nov 15;63(3):1393-403. doi: 10.1016/j.neuroimage.2012.08.027. Epub 2012 Aug 16.
Perceptual decision-making entails the transformation of graded sensory signals into categorical judgments. Often, there is a direct mapping between these judgments and specific motor responses. However, when stimulus-response mappings are fixed, neural activity underlying decision-making cannot be separated from neural activity reflecting motor planning. Several human neuroimaging studies have reported changes in brain activity associated with perceptual decisions. Nevertheless, to date it has remained unknown where and how specific choices are encoded in the human brain when motor planning is decoupled from the decision process. We addressed this question by having subjects judge the direction of motion of dynamic random dot patterns at various levels of motion strength while measuring their brain activity with fMRI. We used multivariate decoding analyses to search the whole brain for patterns of brain activity encoding subjects' choices. To decouple the decision process from motor planning, subjects were informed about the required motor response only after stimulus presentation. Patterns of fMRI signals in early visual and inferior parietal cortex predicted subjects' perceptual choices irrespective of motor planning. This was true across several levels of motion strength and even in the absence of any coherent stimulus motion. We also found that the cortical distribution of choice-selective brain signals depended on stimulus strength: While visual cortex carried most choice-selective information for strong motion, information in parietal cortex decreased with increasing motion coherence. These results demonstrate that human visual and inferior parietal cortex carry information about the visual decision in a more abstract format than can be explained by simple motor intentions. Both brain regions may be differentially involved in perceptual decision-making in the face of strong and weak sensory evidence.
知觉决策涉及将分级的感觉信号转换为分类判断。通常，这些判断与特定的运动反应之间存在直接映射。然而，当刺激-反应映射固定时，决策背后的神经活动不能与反映运动规划的神经活动分开。几项人类神经影像学研究报告了与知觉决策相关的大脑活动变化。然而，迄今为止，当运动规划与决策过程解耦时，人类大脑中特定选择是如何编码的仍然未知。我们通过让受试者在不同的运动强度水平下判断动态随机点模式的运动方向来解决这个问题，同时使用 fMRI 测量他们的大脑活动。我们使用多元解码分析在整个大脑中搜索编码受试者选择的大脑活动模式。为了将决策过程与运动规划解耦，只有在呈现刺激后，受试者才会被告知所需的运动反应。早期视觉和下顶叶皮层的 fMRI 信号模式预测了受试者的知觉选择，而与运动规划无关。这在几个运动强度水平上都是如此，甚至在没有任何一致的刺激运动的情况下也是如此。我们还发现，选择选择性大脑信号的皮质分布取决于刺激强度：虽然视觉皮层对强运动携带了大部分选择选择性信息，但随着运动一致性的增加，顶叶皮层中的信息减少。这些结果表明，人类视觉和下顶叶皮层以比简单的运动意图更抽象的形式携带关于视觉决策的信息。在面对强和弱的感觉证据时，两个大脑区域可能在知觉决策中都有不同的参与。
