Miller Jae-eun Kang, Ayzenshtat Inbal, Carrillo-Reid Luis, Yuste Rafael
Department of Biological Sciences, Columbia University, New York, NY 10027
Department of Biological Sciences, Columbia University, New York, NY 10027.
Proc Natl Acad Sci U S A. 2014 Sep 23;111(38):E4053-61. doi: 10.1073/pnas.1406077111. Epub 2014 Sep 8.
The cortical microcircuit is built with recurrent excitatory connections, and it has long been suggested that the purpose of this design is to enable intrinsically driven reverberating activity. To understand the dynamics of neocortical intrinsic activity better, we performed two-photon calcium imaging of populations of neurons from the primary visual cortex of awake mice during visual stimulation and spontaneous activity. In both conditions, cortical activity is dominated by coactive groups of neurons, forming ensembles whose activation cannot be explained by the independent firing properties of their contributing neurons, considered in isolation. Moreover, individual neurons flexibly join multiple ensembles, vastly expanding the encoding potential of the circuit. Intriguingly, the same coactive ensembles can repeat spontaneously and in response to visual stimuli, indicating that stimulus-evoked responses arise from activating these intrinsic building blocks. Although the spatial properties of stimulus-driven and spontaneous ensembles are similar, spontaneous ensembles are active at random intervals, whereas visually evoked ensembles are time-locked to stimuli. We conclude that neuronal ensembles, built by the coactivation of flexible groups of neurons, are emergent functional units of cortical activity and propose that visual stimuli recruit intrinsically generated ensembles to represent visual attributes.
皮质微电路由反复的兴奋性连接构建而成，长期以来人们一直认为这种设计的目的是实现内在驱动的回响活动。为了更好地理解新皮质内在活动的动力学，我们在视觉刺激和自发活动期间对清醒小鼠初级视觉皮层的神经元群体进行了双光子钙成像。在这两种情况下，皮质活动都由共同激活的神经元群体主导，形成了一些集合，其激活不能用孤立考虑的单个神经元的独立放电特性来解释。此外，单个神经元可以灵活地加入多个集合，极大地扩展了电路的编码潜力。有趣的是，相同的共同激活集合可以自发重复并对视觉刺激做出反应，这表明刺激诱发的反应源于激活这些内在的构建模块。虽然刺激驱动的集合和自发集合的空间特性相似，但自发集合以随机间隔活动，而视觉诱发集合则与刺激时间锁定。我们得出结论，由灵活的神经元群体共同激活构建的神经元集合是皮质活动的新兴功能单元，并提出视觉刺激招募内在产生的集合来表征视觉属性。
