AUTHOR=Papaioannou Stylianos , Medini Paolo 

TITLE=Advantages, Pitfalls, and Developments of All Optical Interrogation Strategies of Microcircuits in vivo

JOURNAL=Frontiers in Neuroscience

VOLUME=Volume 16 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2022.859803

DOI=10.3389/fnins.2022.859803

ISSN=1662-453X

ABSTRACT=The holy grail for every neurophysiologist is to conclude a causal relationship between an elementary  behavior and the function of a specific brain area or circuit. Our effort to map elementary behaviors to specific brain loci and to further manipulate neural activity while observing the alterations in behavior is in essence the goal for neuroscientists. Recent advancements in the area of experimental brain imaging in the form of longer wavelength near infrared (NIR) pulsed lasers with the development of highly efficient optogenetic actuators and reporters of neural activity, has endowed us with unprecedented resolution in spatiotemporal precision both in imaging neural activity as well as manipulating it with multiphoton microscopy. This readily available toolbox has introduced a so called all-optical physiology and interrogation of circuits and has opened new horizons when it comes to precisely, fast and non-invasively map and manipulate anatomically, molecularly or functionally-identified mesoscopic brain circuits. The purpose of this review is to describe the advantages and possible pitfalls of all-optical approaches in system neuroscience, where by all-optical we mean use of multiphoton microscopy to attain flexible choice of the cells to be imaged and/or stimulated. Spatio-temporal constraints will be compared towards the classical reference of electrophysiology methods. When appropriate, in relation to current limitations of current optical approaches, we will make reference to latest works aimed to overcome these limitations, in order to highlight the most recent developments. We will also provide examples of types of experiments uniquely approachable all-optically. Finally, although mechanically non-invasive, all-optical electrophysiology exhibits potential off-target effects which can ambiguate and complicate the interpretation of the results. In summary, this review is an effort to exemplify how an all-optical experiments can be designed, conducted and interpreted from the point of view of the integrative neurophysiologist.