A better platform to image neuronal activity in brain development models

In lieu of studying a full brain, stem cell-derived human cortical organoids (hCOs) have emerged as simpler models for studying brain development. Because the tissues are 3D, normal flat imaging cannot capture the complex dynamics of hCO cells, so volumetric calcium imaging is used to monitor neuronal activities.

Traditional light-field microscopy (LFM) can image large volumes quickly; however, retrieving spatiotemporal calcium activities of hCOs for long-term analysis is challenging since the technique suffers from out-of-focus background noise in thick volumetric specimens. Min et al. combined multiple approaches to better monitor calcium.

“Our approach preserves the single-shot volumetric advantage of LFM while using annular scanning to effectively reduce background noise via the illumination and collection process,” said author Moonseok Kim. “Therefore, it is especially useful for sustained, low-phototoxic functional imaging of organoid-scale specimens where scan-free volumetric acquisition is important.”

The researchers’ platform combines three techniques: LFM to capture the 3D calcium dynamics; annular scanning (AS) to increase the accuracy of LFM and reduce out-of-focus fluorescence; and finally, deep learning algorithms to remove image noise.

“Together, AS-LFM, the optical and computational imaging platform allows low-phototoxic, scan-free volumetric calcium imaging with several-fold enhancement of signal-to-noise ratio in live human cortical organoids,” said Kim.

The researchers see their platform being used to minimize optical aberrations and extend imaging depth. They plan to improve the processing time of their deep learning algorithms.

“Biologically, we aim to apply this platform to larger organoid datasets, disease-model organoids, and drug response studies, where long-term 3D functional readouts could provide more informative measures of human neural circuit development and dysfunction,” said Kim.

Source: “Noninvasive rapid observation of volumetric calcium transients in human cortical organoids using light field microscopy with annular scanning,” by Cheol Hong Min, Seungwon Jeong, Jeong-Sun Choi, Sangjun Park, Hyun-jong Jang, Kyung-Ok Cho, and Moonseok Kim, APL Photonics (2026). The article can be accessed at https://doi.org/10.1063/5.0332998 .