Picot, A. et al. Cell Rep. 24, 1243–1253 (2018).
Two-photon-based optogenetic manipulation of individual cells or ensembles of cells is a valuable approach for analyzing neuronal circuits. However, the necessary illumination schemes can heat up the targeted cells, and this has to be carefully evaluated. Picot et al. describe a model for predicting temperature increases with high spatial and temporal resolution. The researchers validated their model with phantom preparations and then applied it to illumination schemes that are in current experimental use, such as holographic illumination and spiral scanning. They found that illumination designed to optogenetically activate single cells or ensembles of up to 100 cells (using the opsin CoChR) did not lead to local temperature increases beyond 1 K, provided that the cells were not too close together and that the illumination frequency allowed for a sufficient temperature decay between pulses. The scripts used for the modeling are available and should be useful to others who want to evaluate their own experimental conditions.
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Vogt, N. Modeling temperature during optogenetic illumination. Nat Methods 15, 763 (2018). https://doi.org/10.1038/s41592-018-0155-3