Widefield calcium imaging has recently emerged as a powerful experimental technique to record coordinated large-scale brain activity. These measurements present a unique opportunity to characterize spatiotemporally coherent structures that underlie neural activity across many regions of the brain. In this work, we leverage analytic techniques from fluid dynamics to develop a visualization framework that highlights features of flow across the cortex, mapping wavefronts that may be correlated with behavioural events. First, we transform the time series of widefield calcium images into time-varying vector fields using optic flow. Next, we extract concise diagrams summarizing the dynamics, which we refer to as FLOW (flow lines in optical widefield imaging) portraits. These FLOW portraits provide an intuitive map of dynamic calcium activity, including regions of initiation and termination, as well as the direction and extent of activity spread. To extract these structures, we use the finite-time Lyapunov exponent technique developed to analyse time-varying manifolds in unsteady fluids. Importantly, our approach captures coherent structures that are poorly represented by traditional modal decomposition techniques. We demonstrate the application of FLOW portraits on three simple synthetic datasets and two widefield calcium imaging datasets, including cortical waves in the developing mouse and spontaneous cortical activity in an adult mouse.

宽场钙成像最近已成为记录协调的大规模大脑活动的强大实验技术。这些测量提供了一个独特的机会来表征大脑许多区域神经活动的时空相干结构。在这项工作中，我们利用流体动力学的分析技术来开发一个可视化框架，突出显示大脑皮层的流动特征，绘制可能与行为事件相关的波前。首先，我们使用光流将宽场钙图像的时间序列转换为时变矢量场。接下来，我们提取总结动态的简明图表，我们将其称为FLOW（光学宽场成像中的流线）肖像。这些 FLOW 肖像提供了动态钙活性的直观图，包括起始和终止区域，以及活性扩散的方向和程度。为了提取这些结构，我们使用有限时间李亚普诺夫指数技术来分析非稳态流体中的时变流形。重要的是，我们的方法捕获了传统模态分解技术很难表示的相干结构。我们演示了 FLOW 肖像在三个简单的合成数据集和两个宽场钙成像数据集上的应用，包括发育中小鼠的皮质波和成年小鼠的自发皮质活动。