br Conclusion In this article we

Conclusion In this article we detailed the gist of the optogenetic method, its main components and application areas. This method is currently being rapidly developed and improved, and applied in an increasing number of scientific areas. Taking the optogenetic approach to studying various neurodegenerative diseases is of the greatest interest to the authors. For example, in 2013, the abnormalities of synaptic transmission in a cortical and striatal neuronal culture were demonstrated on mouse models of Huntington\'s disease using the optogenetic method [45]. Studying this type of problem is the subject of the authors\' current and future research.
Acknowledgment
The part of the study dedicated to staging and testing optogenetic methods is supported by the Russian Scientific Fund grant no. 14-25-0024.
Introduction It is commonly assumed that each separate group of neurons is responsible for performing some specific elementary function, and it is precisely the interaction between these system units that ensures the functioning of the whole neural network. Up until recently, obtaining experimental data amounted to, primarily, studying the disorders occurring through injuries of certain parts of the brain, or to recording SW033291 activity while experimental subjects performed stereotypical tasks [7]. The researchers most commonly used electrical stimulation and pharmacological compounds for therapeutic treatment [3]. To activate various regions of the brain, electrodes were implanted into them. However, in this case the current affected practically all undifferentiated groups of neurons (since electrodes excites all nervous tissues), and, as a result, it was extremely hard to localize the source generating one function or another. When pharmacological compounds capable of selectively inhibiting neurons of a specific group were used, the effect of chemical substances significantly differed in that it lasted longer compared to natural stimulation [7]. Optogenetics incorporated a fundamentally new practical approach to studying the functioning of brain neurons [3]. This method of neurophysiological research arose as straddling the line between two rapidly evolving fields of research. The genetic component of optogenetic experiments ensures the formation of light-sensitive ion channels in membranes of living cells, while optical equipment and technical devices deliver illumination to predetermined brain regions with high precision (in vivo experiments) and influence cell cultures in vitro. Over time the optogenetic methods have increasingly been used for studying and stimulating not only brain cells but also other organs formed by excitable tissues (e.g., cardiac muscle) [2].
The optogenetic research method
Generation and delivery of light into nervous tissues In early initial experiments the light from a laser or a LED source was transmitted via optical fiber to a neuronal cell culture, tissue segment, or directly into the brain of an immobilized or a freely moving animal (a mouse, a rat, or a monkey) [3]. Over time, as the experiments grew in number and variety, this simple optical line evolved into a complex system of fiber optical devices. Now this advanced network may include (for the case of in vivo experiments), apart from the illumination source and the optical fiber, optical splitters, combiners, swivel joints for experiments with freely moving laboratory animals, various fiber optic light guides, as well as cannulas implanted into brain tissues. All of this engenders the wide array of problems and the variability of the optogenetic method [10]. Critical advantages of the optogenetic method are its selectivity in the problem of affecting a specific brain region or a group of neurons, and its speed in solving the stimulus-result problem. Temporal resolutions with precision to within milliseconds allow to conduct experiments at the speed of the biological response of living cells, for example, when determining the role of specific effects of experimental models in neurons [3].