Numbers and letters are culturally created symbols which are learned through repeated training. This experience leads to a functional specialization of the perceptual system of our brain. Recent evidence suggests a neural dissociation between these two symbols. While previous literature has shown that letters elicit a left lateralized neural response, new studies suggest that numbers elicit preferentially a bilateral or right lateralized response. However, the time course of the neural patterns that characterize this dissociation is still underspecified. In the present study, we investigated with magnetoencephalography (MEG) the spatio-temporal dynamics of the neural response generated by numbers, letters and perceptually matched false fonts presented visually. Twenty-five healthy adults were recorded while participants performed a dot detection task. By including two experiments, we were able to study the effects of single characters as well as those of strings of characters. The signal analysis was focused on the event related fields (ERF) of the MEG signal in the sensors and in the source space. The main results of our study showed an early (<200 msec) preferential dissociation between single numbers and single letters on occipito-temporal sensors. When comparing strings of numbers and pseudowords, they differed also over prefrontal regions of the brain. These data offer a new example of acquired category-specific responses in the human brain.

数字和字母是文化创造的符号，可以通过反复培训来学习。这种经验导致我们大脑的知觉系统功能上的专业化。最近的证据表明这两个符号之间存在神经分离。尽管先前的文献表明字母引起左偏侧神经反应，但新的研究表明数字优先引起双侧或右偏侧神经反应。然而，表征这种解离的神经模式的时程仍未明确。在本研究中，我们用脑磁图（MEG）研究了由数字，字母和视觉上匹配的假字体产生的神经反应的时空动态。参与者执行点检测任务时，记录了25名健康成年人。通过包括两个实验，我们能够研究单个字符以及字符串的影响。信号分析的重点是传感器和源空间中MEG信号的事件相关字段（ERF）。我们研究的主要结果表明，在枕叶时间传感器上，单个数字和单个字母之间的早期（<200毫秒）优先分离。比较数字字符串和伪单词时，它们在大脑的前额叶区域也不同。这些数据提供了人脑中获得的特定类别反应的新示例。信号分析的重点是传感器和源空间中MEG信号的事件相关字段（ERF）。我们研究的主要结果表明，在枕叶时间传感器上，单个数字和单个字母之间的早期（<200毫秒）优先分离。比较数字字符串和伪单词时，它们在大脑的前额叶区域也不同。这些数据提供了人脑中获得的特定类别反应的新示例。信号分析的重点是传感器和源空间中MEG信号的事件相关字段（ERF）。我们研究的主要结果表明，在枕叶时间传感器上，单个数字和单个字母之间的早期（<200毫秒）优先分离。比较数字字符串和伪单词时，它们在大脑的前额叶区域也不同。这些数据提供了人脑中获得的特定类别反应的新示例。