Oxford University, Department of Experimental Psychology, Oxford, UK.
Neuroimage. 2011 Jun 1;56(3):1540-5. doi: 10.1016/j.neuroimage.2011.02.071. Epub 2011 Mar 3.
In this study, we show that top-down control mechanisms engaged during visual imagery of simple shapes (letters X and O) can selectively activate position-invariant perceptual codes in visual areas specialised for shape processing, including lateral occipital complex (LOC). First, we used multivoxel pattern analysis (MVPA) to identify visual cortical areas that code for shape within a position-invariant reference frame. Next, we examined the similarity between these high-level visual codes and patterns elicited while participants imagined the corresponding stimulus at central fixation. Our results demonstrate that imagery engages object-centred codes in higher-level visual areas. More generally, our results also demonstrate that top-down control mechanisms are able to generate highly specific patterns of visual activity in the absence of corresponding sensory input. We argue that a general model of top-down control must account for dynamic modulation of functional connectivity between high-level control centres and overlapping neural codes in visual cortex.
在这项研究中，我们表明，在对简单形状（字母 X 和 O）进行视觉想象时，自上而下的控制机制可以选择性地激活专门用于形状处理的视觉区域中的位置不变知觉代码，包括外侧枕叶复合体（LOC）。首先，我们使用多体素模式分析（MVPA）来识别在位置不变参考框架内编码形状的视觉皮层区域。接下来，我们检查了这些高级视觉代码与参与者在中央注视点想象相应刺激时引起的模式之间的相似性。我们的结果表明，想象活动在更高层次的视觉区域中使用以对象为中心的代码。更一般地说，我们的结果还表明，自上而下的控制机制能够在没有相应感觉输入的情况下产生高度特定的视觉活动模式。我们认为，自上而下的控制的一般模型必须解释高级控制中心和视觉皮层中重叠的神经代码之间功能连接的动态调制。
