# Continuous Dynamic Photostimulation - inducing in-vivo-like fluctuating conductances with Channelrhodopsins

**Authors:** Andreas Neef, Ahmed El Hady, Jatin Nagpal, Kai Bröking, Ghazaleh Afshar, Oliver M Schlüter, Theo Geisel, Ernst Bamberg, Ragnar Fleischmann, Walter Stühmer, Fred Wolf  
**arXiv:** [1305.7125](https://arxiv.org/abs/1305.7125)  
**Date:** 2013-05-30  
**Summary page:** https://www.summarizepaper.com/en/paper/1305.7125v2/

## Key points

- Study focuses on operation of central neurons influenced by fluctuating conductances induced by presynaptic cells
- Traditional method uses channelrhodopsins for fixed spike pattern through depolarizations
- Novel approach called continuous dynamic photostimulation (CoDyPs) mimics in-vivo-like input fluctuations noninvasively
- Weakly inactivating channelrhodopsin variant called ChIEF used in transfected cells
- CoDyPs induces seemingly random but reproducible spike patterns in cultured neurons
- CoDyPs can replace conventional flash-evoked imprinting of spike patterns while preserving natural activity
- Combined with non-invasive spike-detection techniques, CoDyPs enables acquisition of larger datasets
- Allows for more comprehensive studies on dynamical response properties of individual neurons at a larger scale
- Innovative method for studying neuronal activity by replicating natural input fluctuations using continuous dynamic photostimulation

## Summary

The study focuses on the operation of central neurons, which are constantly influenced by fluctuating conductances induced by thousands of presynaptic cells. Traditionally, channelrhodopsins have been used to impose a fixed spike pattern through brief depolarizations. However, this study introduces a novel approach called continuous dynamic photostimulation (CoDyPs) that mimics in-vivo-like input fluctuations noninvasively. The researchers transfected cells with a weakly inactivating channelrhodopsin variant called ChIEF and subjected cultured neurons to CoDyPs. They found that even during long-term experiments, these neurons generated seemingly random but reproducible spike patterns. In voltage clamped cells, CoDyPs induced highly reproducible current waveforms that could be accurately predicted from the light-conductance transfer function of ChIEF. CoDyPs has the potential to replace conventional flash-evoked imprinting of spike patterns in both in-vivo and in-vitro studies while preserving natural activity. When combined with non-invasive spike-detection techniques, CoDyPs enables the acquisition of significantly larger datasets than previously possible. This allows for more comprehensive studies on the dynamical response properties of many individual neurons and provides an invaluable tool for investigating the response properties of individual neurons at a larger scale. Overall, this research presents an innovative method for studying neuronal activity by replicating natural input fluctuations using continuous dynamic photostimulation. The findings have implications for understanding how central neurons operate under constantly changing conditions and offer a valuable tool for exploring the response properties of individual neurons at a larger scale.