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Brain-wide recording of neural activity at single-cell resolution using SPIM-based calcium imaging
The optical transparency and the small dimensions of zebrafish at the larval stage make it a vertebrate model of choice for brain-wide in-vivo functional imaging. However, current point-scanning imaging techniques, such as two-photon or confocal microscopy, impose a strong limit on acquisition speed which in turn sets the number of neurons that can be simultaneously recorded. At 5Hz, this number is of the order of one thousand, i.e. approximately 1% of the brain. In this talk, I will show that Selective-plane Illumination Microscopy (SPIM) allows for a 20-fold increase in data throughput with comparable SNR : the long-term spontaneous activity of up to 5000 neurons at 20Hz and 25000 neurons (roughly 30% of the brain volume) at 4Hz was recorded in larvae expressing the genetically encoded calcium indicator GCaMP3. The extended field of view offered by SPIM allowed us to directly identify large scale ensembles of neurons, spanning several brain regions, that displayed correlated activity and were thus likely to participate in common neural processes. The benefits and limitations of SPIM for functional imaging in zebrafish as well as future developments will be discussed.