Available experimental techniques
Cranial window implantation
Cranial window enables access to the brain for long-term in vivo imaging. Cranial window implantation is a surgical procedure, during which a part of the skull is removed and the exposed area is subsequently sealed with a glass coverslip. The coverslip is attached to the bone using dental cement. At the same time, a metal bar is attached to the bone to allow for fixation of the animal in the microscope during subsequent imaging.
The cranial window can be placed over an area of interest. The areas studied in the laboratory involve auditory cortex and inferior colliculus of a mouse.
Viral injection involves injecting a genetically modified virus to a selected part of the animal tissue. Viruses used in the lab are AAVs expressing GCaMP receptors and/or rhodopsins used for optogenetics.
Optogenetics is a method enabling targeted activation or inhibition of specific cell populations using light. The modulation is enabled by expressing light-gated ion channels in the cells of interests transduced via a viral vector. Therefore, the lasers in the microscope can be used both for optogenetic modulation and for subsequent recording of the signal.
Imaging can be also combined with chemogenetics. As with optogenetics, chemogenetics allows activating or inhibiting specific cell populations. However, the mode of activation is different and the effects are usually more long-lasting and slower to start. The receptors enabling chemogenetic modulation (DREADDs) are expressed in the populations of interest and can be activated using small, otherwise inert molecules, such as CNO. The expression of the receptors is enabled via viral vectors.