Genetically Encoded Voltage Indicators (GEVIs)

* Engineered light-emitting protein sensors
* Combines the advantages of light and genetics to track neuronal voltage dynamics
* Optimally bright, photostable and less cytotoxic
* Use the same wavelengths and equipment as used for imaging calcium indicators
* Direct measurement of neuronal electrical activity with cellular resolution and increased fidelity
* Less invasive, better targeted, and greater multisite monitoring of neuronal activity
* Monitoring the voltage dynamics of individual neurons, from synaptic inputs to axonal outputs, is critical for understanding the neural processes that underlie behavior
* Imaging can allow tracking of voltage signals with higher spatial resolution and from multiple subcellular locations, neighboring neurons, or brain areas. Optical methods can also more easily record voltage from small subcellular areas, such as dendritic spines

* To report neuronal voltage dynamics as changes in brightness

* Measured electrical activity in Drosophila mushroom body output neuron dendrites and Kenyon cell axons and identified new sleep-promoting and wake-promoting cells and microcircuits
* Small size of the fly brain and restricted GEVI expression allows cellular resolution optical recordings with wide-field microscopy
* Tracking spiking activity in one or more cortical neurons down to layer V of awake behaving mouse for extended durations (>30 min)

* In situ physiological studies in all key model systems as worms, zebrafish, Drosophila, mice

* Applicable on wide model systems and/or imaging modalities
* Compatible for in vivo applications with microscopy techniques for deep tissue imaging
* Show neuron signals with subcellular spatial resolution
* Compatible for measuring large-scale voltage dynamics
* Utilizes cell type-specific promoters for selective labeling of specific cell types

* Differential expression and/or performance of GEVIs in different model systems
* Many optical techniques only enable imaging signals of a few individual neurons simultaneously in vivo
* No current method has shown robust voltage optical recording in three-dimension in awake behaving mice

* Should detect individual spikes (including in bursts) and small hyperpolarizations and subthreshold depolarizations
* Should be sensitive and efficient
* Should be compatible with available imaging modalities (single or two photon microscopy methods)

* https://www.stpierrelab.com/publications

* https://neuronex.org/projects/8

* https://www.jove.com/search?q=GEVIs&filter_type_1=and&filter_val_1=&filter_type_2=and&filter_val_2=&filter_type_3=not&filter_val_3=&authors=&from=&to=&exclude_sections=&exclude_series=

* https://www.braininitiative.org/events/sfn-social/

* Molecular chimeras between voltage sensitive and optical (i.e. fluorescent) proteins

* https://www.bcm.edu/people/view/francois-st-pierre-ph-d/ce5139a8-20f1-11e5-8d53-005056b104be