School of Psychology, University of Birmingham, Birmingham B15 2TT, United Kingdom.
J Neurosci. 2012 Jan 18;32(3):775-86. doi: 10.1523/JNEUROSCI.2033-11.2012.
Learning is known to facilitate our ability to detect targets in clutter and optimize brain processes for successful visual recognition. Previous brain-imaging studies have focused on identifying spatial patterns (i.e., brain areas) that change with learning, implicating occipitotemporal and frontoparietal areas. However, little is known about the interactions within this network that mediate learning-dependent improvement in complex perceptual tasks (i.e., discrimination of visual forms in clutter). Here we take advantage of the complementary high spatial and temporal resolution of simultaneous EEG-fMRI to identify the learning-dependent changes in spatiotemporal brain patterns that mediate enhanced behavioral sensitivity in the discrimination of global forms after training. We measured the observers' choices when discriminating between concentric and radial patterns presented in noise before and after training. Similarly, we measured the choices of a pattern classifier when predicting each stimulus from EEG-fMRI signals. By comparing the performance of human observers and classifiers, we demonstrated that learning alters sensitivity to visual forms and EEG-fMRI activation patterns related to distinct visual recognition processes. In particular, behavioral improvement after training was associated with changes in (1) early processes involved in the integration of global forms in higher occipitotemporal and parietal areas, and (2) later processes related to categorical judgments in frontal circuits. Thus, our findings provide evidence that learning acts on distinct visual recognition processes and shapes feedforward interactions across brain areas to support performance in complex perceptual tasks.
学习被认为可以提高我们在混杂环境中检测目标的能力，并优化大脑处理过程，以实现成功的视觉识别。先前的脑成像研究集中于识别随学习而变化的空间模式（即大脑区域），这些模式涉及枕颞和额顶区域。然而，对于介导复杂感知任务（即在混杂中辨别视觉形式）中学习依赖性改善的网络内相互作用，我们知之甚少。在这里，我们利用 EEG-fMRI 的互补高空间和时间分辨率，来识别在训练后提高复杂感知任务中辨别全局形状的行为敏感性时，介导时空大脑模式变化的学习依赖性变化。我们在训练前后的噪声中测量了观察者在辨别同心和放射模式时的选择。同样，我们还测量了模式分类器在根据 EEG-fMRI 信号预测每个刺激时的选择。通过比较人类观察者和分类器的性能，我们证明了学习改变了对视觉形式的敏感性，以及与不同视觉识别过程相关的 EEG-fMRI 激活模式。具体来说，训练后的行为改善与以下方面的变化有关：（1）与更高的枕颞和顶叶区域中全局形式的整合有关的早期过程；（2）与额叶回路中的类别判断有关的后期过程。因此，我们的发现提供了证据表明，学习作用于不同的视觉识别过程，并塑造了跨大脑区域的前馈相互作用，以支持复杂感知任务的表现。
