The neural representation of Arabic digits in visual cortex
The neural representation of Arabic digits in visual cortex
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DOI：
10.3389/fnhum.2015.00517
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发表时间：
2015-09-24
影响因子：
2.9
通讯作者：
Op de Beeck, Hans P.
中科院分区：
文献类型：
--
作者：
Peters, Lien;De Smedt, Bert;Op de Beeck, Hans P.
在这项研究中，我们研究了阿拉伯数字是如何在视觉皮层中表示的，以及它们的表示在整个腹侧视觉处理流中的变化，与字母的表示相比。我们用两个功能性磁共振成像（fMRI）实验来探讨这些问题。在实验1中，我们探索了在减法任务中，我们是否能找到对数字比数字词更活跃的大脑区域。在枕叶外侧皮质中检测到一个这样的区域。但是，此区域中的活动可能受到字符串长度数字字包含的字符多于数字的干扰。因此，我们进行了第二个实验，在这个实验中，弦的长度被系统地控制。实验2表明，第一个实验的结果是任务依赖的（因为它只在任务中观察到的数字是相关的）或刺激依赖的（因为它只观察到的刺激字符的数量不受控制）。通过多体素模式分析，我们进一步探讨了数字和字母串在腹侧视觉加工流中激活模式的特点。我们发现，在整个腹侧处理流的表示从集群的基础上的视觉信息量在初级视觉皮层（V1）对集群的基础上更高的视觉层次结构中的符号刺激类别的变化。目前的研究结果收敛的结论是，在腹侧视觉系统中，尽可能可以检测到与功能磁共振成像，阿拉伯数字和字母串之间的区别是代表在分布式模式，而不是单独的区域。
In this study, we investigated how Arabic digits are represented in the visual cortex, and how their representation changes throughout the ventral visual processing stream, compared to the representation of letters. We probed these questions with two functional magnetic resonance imaging (fMRI) experiments. In Experiment 1, we explored whether we could find brain regions that were more activated for digits than for number words in a subtraction task. One such region was detected in lateral occipital cortex. However, the activity in this region might have been confounded by string length number words contain more characters than digits. We therefore conducted a second experiment in which string length was systematically controlled. Experiment 2 revealed that the findings of the first experiment were task dependent (as it was only observed in a task in which numerosity was relevant) or stimulus dependent (as it was only observed when the number of characters of a stimulus was not controlled). We further explored the characteristics of the activation patterns for digit and letter strings across the ventral visual processing stream through multi-voxel pattern analyses. We found an alteration in representations throughout the ventral processing stream from clustering based on amount of visual information in primary visual cortex (V1) towards clustering based on symbolic stimulus category higher in the visual hierarchy. The present findings converge to the conclusion that in the ventral visual system, as far as can be detected with fMRI, the distinction between Arabic digits and letter strings is represented in terms of distributed patterns rather than separate regions.