The internal brain dynamics that link sensation and action are arguably better studied during natural animal behaviors. Here, we report on a novel volume imaging and 3D tracking technique that monitors whole brain neural activity in freely swimming larval zebrafish (Danio rerio). We demonstrated the capability of our system through functional imaging of neural activity during visually evoked and prey capture behaviors in larval zebrafish.

23The internal brain dynamics that link sensation and action are arguably better studied 24 during natural animal behaviors. Here we report on a novel volume imaging and 3D 25 tracking technique that monitors whole brain neural activity in freely swimming larval 26 zebrafish (Danio rerio). We demonstrated the capability of our system through functional 27 imaging of neural activity during visually evoked and prey capture behaviors in larval 28 zebrafish. 29 30 31

One of the major challenges in large scale optical imaging of neuronal activity is to simultaneously achieve sufficient temporal and spatial resolution across a large volume. Here, we introduce sparse decomposition light-field microscopy (SDLFM), a computational imaging technique based on light-field microscopy (LFM) that takes algorithmic advantage of the high temporal resolution of LFM and the inherent temporal sparsity of spikes to improve effective spatial resolution and signal-to-noise ratios (SNRs). With increased effective spatial resolution and SNRs, neuronal activity at the single-cell level can be recovered over a large volume. We demonstrate the single-cell imaging capability of SDLFM with in vivo imaging of neuronal activity of whole brains of larval zebrafish with estimated lateral and axial resolutions of ∼ 3.5 µ m and ∼ 7.4 µ m , respectively, acquired at volumetric imaging rates up to 50 Hz. We also show that SDLFM increases the quality of neural imaging in adult fruit flies.

Monitoring and manipulating neuronal activities with optical microscopy desires a method where light can be focused or projected over a long axial range so that large brain tissues (>100 [Formula: see text] thick) can be simultaneously imaged, and specific brain regions can be optogenetically stimulated without the need for slow optical refocusing. However, the micron-scale resolution required in neuronal imaging yields a depth of field of less than 10 [Formula: see text] in conventional imaging systems. We propose to use a circularly symmetric phase mask to extend the depth of field. A numerical study shows that our method maintains both the peak and the shape of the point spread function vs the axial position better than current methods. Imaging of a 3D bead suspension and sparsely labelled thick brain tissue confirms the feasibility of the system for fast volumetric imaging.

Molecular signals interact to mediate diverse biological computations. Ideally one would be able to image many signals at once, in the same living cell, to reveal how they work together. Here we report temporally multiplexed imaging (TMI), which uses the clocklike properties of fluorescent proteins to enable different cellular signals to be represented by different temporal fluorescence codes. Using different photoswitchable fluorescent proteins to represent different cellular signals, we can linearly decompose a brief movie of the fluorescence fluctuations in a given cell, into a sum of the fluctuation traces of each individual fluorophore, each weighted by its respective signal amplitude. We demonstrate the power of TMI to report relationships amongst a diversity of second messenger, kinase, and cell cycle signals, using ordinary microscopes.

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