Department of Biomedicine, University of Basel, Basel, Switzerland.
Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
Nat Commun. 2021 Apr 26;12(1):2438. doi: 10.1038/s41467-021-22421-8.
Cortical and limbic brain areas are regarded as centres for learning. However, how thalamic sensory relays participate in plasticity upon associative learning, yet support stable long-term sensory coding remains unknown. Using a miniature microscope imaging approach, we monitor the activity of populations of auditory thalamus (medial geniculate body) neurons in freely moving mice upon fear conditioning. We find that single cells exhibit mixed selectivity and heterogeneous plasticity patterns to auditory and aversive stimuli upon learning, which is conserved in amygdala-projecting medial geniculate body neurons. Activity in auditory thalamus to amygdala-projecting neurons stabilizes single cell plasticity in the total medial geniculate body population and is necessary for fear memory consolidation. In contrast to individual cells, population level encoding of auditory stimuli remained stable across days. Our data identifies auditory thalamus as a site for complex neuronal plasticity in fear learning upstream of the amygdala that is in an ideal position to drive plasticity in cortical and limbic brain areas. These findings suggest that medial geniculate body's role goes beyond a sole relay function by balancing experience-dependent, diverse single cell plasticity with consistent ensemble level representations of the sensory environment to support stable auditory perception with minimal affective bias.
大脑皮层和边缘脑区被认为是学习的中心。然而，丘脑感觉中继在联想学习中的参与方式，以及如何支持稳定的长期感觉编码仍然未知。我们使用微型显微镜成像方法，在自由活动的小鼠中监测听觉丘脑（内侧膝状体）神经元群体在恐惧条件反射时的活动。我们发现，单个细胞在学习过程中对听觉和厌恶刺激表现出混合的选择性和异质性的可塑性模式，而在投射到杏仁核的内侧膝状体神经元中则保持不变。听觉丘脑向投射到杏仁核的神经元的活动稳定了整个内侧膝状体神经元群体的单个细胞可塑性，并对恐惧记忆的巩固是必要的。与单个细胞相反，听觉刺激的群体水平编码在几天内保持稳定。我们的数据表明，听觉丘脑在杏仁核上游的恐惧学习中是一个复杂的神经元可塑性的部位，它处于一个理想的位置，可以驱动大脑皮层和边缘脑区的可塑性。这些发现表明，内侧膝状体的作用不仅仅是一个单纯的中继功能，它通过平衡经验依赖性的、多样化的单个细胞可塑性与对感觉环境的一致的整体水平表示，来支持稳定的听觉感知，同时最小化情感偏见。
