McFadyen Jessica, Mermillod Martial, Mattingley Jason B, Halász Veronika, Garrido Marta I
Queensland Brain Institute, The University of Queensland, Brisbane, 4072, QLD, Australia,
Centre for Advanced Imaging, The University of Queensland, Brisbane, 4072, QLD, Australia.
J Neurosci. 2017 Apr 5;37(14):3864-3874. doi: 10.1523/JNEUROSCI.3525-16.2017. Epub 2017 Mar 10.
There is significant controversy over the existence and function of a direct subcortical visual pathway to the amygdala. It is thought that this pathway rapidly transmits low spatial frequency information to the amygdala independently of the cortex, and yet the directionality of this function has never been determined. We used magnetoencephalography to measure neural activity while human participants discriminated the gender of neutral and fearful faces filtered for low or high spatial frequencies. We applied dynamic causal modeling to demonstrate that the most likely underlying neural network consisted of a pulvinar-amygdala connection that was uninfluenced by spatial frequency or emotion, and a cortical-amygdala connection that conveyed high spatial frequencies. Crucially, data-driven neural simulations revealed a clear temporal advantage of the subcortical connection over the cortical connection in influencing amygdala activity. Thus, our findings support the existence of a rapid subcortical pathway that is nonselective in terms of the spatial frequency or emotional content of faces. We propose that that the "coarseness" of the subcortical route may be better reframed as "generalized." The human amygdala coordinates how we respond to biologically relevant stimuli, such as threat or reward. It has been postulated that the amygdala first receives visual input via a rapid subcortical route that conveys "coarse" information, namely, low spatial frequencies. For the first time, the present paper provides direction-specific evidence from computational modeling that the subcortical route plays a generalized role in visual processing by rapidly transmitting raw, unfiltered information directly to the amygdala. This calls into question a widely held assumption across human and animal research that fear responses are produced faster by low spatial frequencies. Our proposed mechanism suggests organisms quickly generate fear responses to a wide range of visual properties, heavily implicating future research on anxiety-prevention strategies.
关于存在一条直接通向杏仁核的皮质下视觉通路及其功能，存在重大争议。人们认为这条通路能独立于皮质，快速将低空间频率信息传递至杏仁核，然而这一功能的方向性从未得到确定。我们利用脑磁图来测量人类参与者在辨别经过低空间频率或高空间频率滤波的中性和恐惧面孔的性别时的神经活动。我们应用动态因果模型来证明，最可能的潜在神经网络由一个不受空间频率或情绪影响的丘脑枕 - 杏仁核连接，以及一个传递高空间频率的皮质 - 杏仁核连接组成。至关重要的是，数据驱动的神经模拟揭示了在影响杏仁核活动方面，皮质下连接相对于皮质连接具有明显的时间优势。因此，我们的研究结果支持存在一条快速的皮质下通路，该通路在面孔的空间频率或情感内容方面是非选择性的。我们提出，皮质下通路的“粗糙性”或许更宜被重新表述为“一般性”。人类杏仁核协调我们对诸如威胁或奖励等生物学相关刺激的反应。据推测，杏仁核首先通过一条快速的皮质下通路接收视觉输入，该通路传递“粗糙”信息，即低空间频率。本文首次从计算模型中提供了方向特异性证据，表明皮质下通路通过将原始的、未经过滤的信息直接快速传递至杏仁核，在视觉处理中发挥着一般性作用。这对人类和动物研究中一个广泛持有的假设提出了质疑，即低空间频率能更快地产生恐惧反应。我们提出的机制表明，生物体能够快速对广泛的视觉属性产生恐惧反应，这对未来焦虑预防策略的研究具有重大意义。
