Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103, Germany,
Department of Psychology and Language Sciences.
J Neurosci. 2018 Jan 31;38(5):1295-1310. doi: 10.1523/JNEUROSCI.0491-17.2017. Epub 2018 Jan 4.
Sensory perception relies on the precise neuronal encoding of modality-specific environmental features in primary sensory cortices. Some studies have reported the penetration of signals from other modalities even into early sensory areas. So far, no comprehensive account of maps induced by "foreign sources" exists. We addressed this question using surface-based topographic mapping techniques applied to ultra-high resolution fMRI neuroimaging data, measured in female participants. We show that fine-grained finger maps in human primary somatosensory cortex, area 3b, are somatotopically activated not only during tactile mechanical stimulation, but also when viewing the same fingers being touched. Visually-induced maps were weak in amplitude, but overlapped with the stronger tactile maps tangential to the cortical sheet when finger touches were observed in both first- and third-person perspectives. However, visually-induced maps did not overlap tactile maps when the observed fingers were only approached by an object but not actually touched. Our data provide evidence that "foreign source maps" in early sensory cortices are present in the healthy human brain, that their arrangement is precise, and that their induction is feature-selective. The computations required to generate such specific responses suggest that counterflow (feedback) processing may be much more spatially specific than has been often assumed. Using ultra-high field fMRI, we provide empirical evidence that viewing touches activates topographically aligned single finger maps in human primary somatosensory cortical area 3b. This shows that "foreign source maps" in early sensory cortices are topographic, precise, and feature-selective in healthy human participants with intact sensory pathways.
感觉知觉依赖于初级感觉皮层中对特定感觉模态环境特征的精确神经元编码。一些研究报告称，即使在早期感觉区域也有来自其他感觉模态的信号渗透。到目前为止，还没有关于“外来源”诱导图谱的综合描述。我们使用基于表面的地形映射技术解决了这个问题，该技术应用于女性参与者的超高分辨率 fMRI 神经影像学数据。我们表明，人类初级体感皮层（3b 区）中的精细手指图谱不仅在触觉机械刺激期间，而且在观察到相同手指被触摸时，也具有体感定位激活。视觉诱导的图谱幅度较弱，但当在第一人称和第三人称视角观察到手指触摸时，与皮质片相切的较强触觉图谱重叠。然而，当观察到的手指只是被物体接近而未实际触摸时，视觉诱导的图谱与触觉图谱不重叠。我们的数据提供了证据表明，早期感觉皮层中的“外来源图谱”存在于健康人脑内，其排列是精确的，其诱导是特征选择性的。产生这种特定反应所需的计算表明，反向流（反馈）处理可能比通常假设的空间特异性更强。我们使用超高场 fMRI 提供了经验证据，表明观察触摸会激活人类初级体感皮层 3b 区中地形对齐的单个手指图谱。这表明，在感觉通路完整的健康人类参与者中，早期感觉皮层中的“外来源图谱”是地形的、精确的和特征选择性的。
