Long-term stability of cortical ensembles

Neuronal ensembles, coactive groups of neurons found in spontaneous and
evoked cortical activity, are causally related to memories and perception,
but it still unknown how stable or flexible they are over time. We used
two-photon multiplane calcium imaging to track over weeks the activity of
the same pyramidal neurons in layer 2/3 of the visual cortex from awake
mice and recorded their spontaneous and visually evoked responses. Less
than half of the neurons were commonly active across any two imaging
sessions. These “common neurons” formed stable ensembles lasting weeks,
but some ensembles were also transient and appeared only in one single
session. Stable ensembles preserved ~68 % of their neurons up to 46 days,
our longest imaged period, and these “core” cells had stronger functional
connectivity. Our results demonstrate that neuronal ensembles can last for
weeks and could, in principle, serve as a substrate for long-lasting
representation of perceptual states or memories.

神经元集合（Neuronal ensembles）是自发与诱发皮层活动中存在的共激活神经元群，与记忆和感知存在因果关联，但其随时间的稳定性或灵活性仍不明确。本研究采用双光子多平面钙成像（two-photon multiplane calcium imaging）技术，连续数周追踪清醒小鼠视觉皮层2/3层中同一批锥体神经元的活动，并记录其自发及视觉诱发反应。任意两次成像会话中，仅有不到一半的神经元存在共同激活；这些“共同神经元”形成了可维持数周的稳定集合，但部分集合具有短暂性，仅在单次会话中出现。稳定集合在最长达46天的成像周期内保留了约68%的神经元，且这些“核心”细胞具有更强的功能连接性。研究结果表明，神经元集合可维持数周，原则上能够作为感知状态或记忆长期表征的基础。