Ultrafast frame-free imaging of neural activity with event cameras.

Frame-based fluorescence imaging has long defined how neural activity is optically measured1. Yet, this approach relies on acquiring all pixels regardless of their dynamics, intrinsically coupling spatial and temporal resolution while increasing data rates. This challenge is particularly acute for voltage imaging, which necessitates precise measurement of fast and distributed signals. Here, we introduce a frame-free approach using event-based cameras, which asynchronously report fluorescence changes as sparse spatiotemporal events. By leveraging the sparsity of neural activity, this method preserves signal fidelity while removing the fixed trade-off between spatial resolution, temporal resolution, and data rate, reducing data output by orders of magnitude. Applied to hippocampal preparations, it resolves single action potentials and fast network dynamics over large fields of view at kilohertz-scale rates, enabling scalable, ultrafast optical recordings.