Department of Psychiatry, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA.
Department of Neurology, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA.
Brain Behav. 2021 Apr;11(4):e02042. doi: 10.1002/brb3.2042. Epub 2021 Jan 22.
The inner voice is experienced during thinking in words (inner speech) and silent reading and evokes brain activity that is highly similar to that associated with external voices. Yet while the inner voice is experienced in internal space (inside the head), external voices (one's own and those of others) are experienced in external space. In this paper, we investigate the neural basis of this differential spatial localization.
We used fMRI to examine the difference in brain activity between reading silently and reading aloud. As the task involved reading aloud, data were first denoised by removing independent components related to head movement. They were subsequently processed using finite impulse response basis function to address the variations of the hemodynamic response. Final analyses were carried out using permutation-based statistics, which is appropriate for small samples. These analyses produce spatiotemporal maps of brain activity.
Reading silently relative to reading aloud was associated with activity of the "where" auditory pathway (Inferior parietal lobule and middle temporal gyrus), and delayed activity of the primary auditory cortex.
These pilot data suggest that internal space localization of the inner voice depends on the same neural resources as that for external space localization of external voices-the "where" auditory pathway. We discuss the implications of these findings on the possible mechanisms of abnormal experiences of the inner voice as is the case in verbal hallucinations.
内言语（在词语思维和默读中体验到的言语）伴随着与外部声音高度相似的大脑活动。然而，虽然内言语发生在内部空间（头部内部），但外部声音（自己和他人的声音）发生在外部空间。在本文中，我们研究了这种空间差异的神经基础。
我们使用 fMRI 研究了默读和朗读时大脑活动的差异。由于该任务涉及朗读，因此首先通过去除与头部运动相关的独立成分来对数据进行去噪。然后使用有限脉冲响应基函数对数据进行处理，以解决血液动力学响应的变化。最后使用适合小样本的置换统计进行分析。这些分析产生了大脑活动的时空图谱。
与朗读相比，默读时听觉“何处”通路（顶下小叶和颞中回）和初级听觉皮层的活动延迟。
这些初步数据表明，内言语的内部空间定位依赖于与外部声音的外部空间定位相同的神经资源——“何处”听觉通路。我们讨论了这些发现对内在声音异常体验的可能机制的影响，如言语幻觉。
