Implications of temporal sampling in voltage imaging microscopy

Significance: Voltage imaging microscopy has emerged as a powerful tool to investigate neural activity both in vivo and in vitro. Various imaging approaches have been developed, including point-scanning, line-scanning and wide-field microscopes, however the effects of their different temporal sampling methods on signal fidelity have not yet been fully investigated. Aim: To provide an analysis of the inherent advantages and disadvantages of temporal sampling in scanning and wide-field microscopes and their effect on the fidelity of voltage spike detection. Approach: We develop a mathematical framework based on a mixture of analytical modeling and computer simulations with Monte-Carlo approaches. Results: Scanning microscopes outperform wide-field microscopes in low signal-to-noise conditions and when only a small subset of spikes needs to be detected. Wide-field microscopes outperform scanning microscopes when the measurement is temporally undersampled and a large fraction of the spikes needs to be detected. Both modalities converge in performance as sampling increases and the frame rate reaches the decay rate of the voltage indicator. Conclusions: Our work provides guidance for the selection of optimal temporal sampling parameters for voltage imaging. Most importantly it advises against using scanning voltage imaging microscopes at frame rates below 500 Hz.

💡 Research Summary

The manuscript presents a comprehensive theoretical and computational investigation of how temporal sampling strategies inherent to different voltage‑imaging microscopes affect the fidelity of spike detection. The authors focus on three major imaging modalities—point‑scanning, line‑scanning, and wide‑field—characterizing each by its duty cycle (τ), i.e., the fraction of a frame during which fluorescence from a cell is actually integrated. In wide‑field systems τ≈1, whereas scanning systems typically have τ≈0.1 because the pixel dwell time is short relative to the frame duration.

Starting from a simple exponential model of a voltage‑indicator response, v(t)=n₀·e⁻ˡᵃᵐᵇ𝑑𝑎·t (t≥0), the authors derive an analytical sampling function s(t) = (v⊗Π_τ)(t), where Π_τ is a rectangular integration window of width τ·d (d is the frame period). Closed‑form expressions for the expected value E