Sharma Saloni, Nelissen Koen
Laboratory for Neuro- & Psychophysiology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium.
Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium.
Brain Sci. 2023 Oct 17;13(10):1466. doi: 10.3390/brainsci13101466.
To probe the presence of mirror neurons in the human brain, cross-modal fMRI adaptation has been suggested as a suitable technique. The rationale behind this suggestion is that this technique allows making more accurate inferences about neural response properties underlying fMRI voxel activations, beyond merely showing shared voxels that are active during both action observation and execution. However, the validity of using cross-modal fMRI adaptation to demonstrate the presence of mirror neurons in parietal and premotor brain regions has been questioned given the inconsistent and weak results obtained in human studies. A better understanding of cross-modal fMRI adaptation effects in the macaque brain is required as the rationale for using this approach is based on several assumptions related to macaque mirror neuron response properties that still need validation. Here, we conducted a cross-modal fMRI adaptation study in macaque monkeys, using the same action execution and action observation tasks that successfully yielded mirror neuron region cross-modal action decoding in a previous monkey MVPA study. We scanned two male rhesus monkeys while they first executed a sequence of either reach-and-grasp or reach-and-touch hand actions and then observed a video of a human actor performing these motor acts. Both whole-brain and region-of-interest analyses failed to demonstrate cross-modal fMRI adaptation effects in parietal and premotor mirror neuron regions. Our results, in line with previous findings in non-human primates, show that cross-modal motor-to-visual fMRI adaptation is not easily detected in monkey brain regions known to house mirror neurons. Thus, our results advocate caution in using cross-modal fMRI adaptation as a method to infer whether mirror neurons can be found in the primate brain.
为探究人类大脑中镜像神经元的存在，跨模态功能磁共振成像适应（cross-modal fMRI adaptation）被认为是一种合适的技术。这一建议背后的基本原理是，该技术不仅能显示在动作观察和执行过程中均活跃的共享体素，还能让人对功能磁共振成像体素激活背后的神经反应特性做出更准确的推断。然而，鉴于在人类研究中获得的结果不一致且微弱，使用跨模态功能磁共振成像适应来证明顶叶和运动前区脑区存在镜像神经元的有效性受到了质疑。由于使用这种方法的基本原理基于一些与猕猴镜像神经元反应特性相关的假设，而这些假设仍需验证，因此需要更好地了解猕猴大脑中的跨模态功能磁共振成像适应效应。在此，我们对猕猴进行了一项跨模态功能磁共振成像适应研究，采用了与之前一项猕猴多体素模式分析（MVPA）研究中成功实现镜像神经元区域跨模态动作解码相同的动作执行和动作观察任务。我们对两只雄性恒河猴进行了扫描，它们先是执行一系列抓握或触摸手部动作，然后观看人类演员执行这些动作的视频。全脑分析和感兴趣区域分析均未能在顶叶和运动前区镜像神经元区域显示出跨模态功能磁共振成像适应效应。我们的结果与之前在非人类灵长类动物中的发现一致，表明在已知存在镜像神经元的猴脑区域中，跨模态运动到视觉的功能磁共振成像适应不易被检测到。因此，我们的结果主张在使用跨模态功能磁共振成像适应作为推断灵长类大脑中是否存在镜像神经元的方法时应谨慎。
