The field of neurobiology is seeing rapid advances in our understanding of neural circuitry in the brain

Question

Part of this work involves the physical mapping of all synapses (a project dubbed the connectome); another critical advance is in the area of optogenetics, which allows scientists to dissect neural circuits that determine specific behaviors in a range of organisms from fruit flies to monkeys.
A. Describe the method of optogenetics.
B. Optogenetics has great potential for deepening our understanding of behavior, learning, memory, and cognitive development. However, it is not as likely to be used directly for treatment of problems such as depression or anxiety. Why not? Consider the limitations of the method when answering this question.

Answer 1

A. Optogenetics is a method in which genetic engineering techniques are used to introduce light-gated channels into a selected set of target neurons. Light of a specific wavelength is then used to open the channel, which allows the investigator to directly control the activity of these neurons in the living organism. When the channels used are light-gated Na+ channels, stimulation will allow Na+ to enter the neurons, triggering an action potential. Light-gated Cl- channels can similarly be used to inhibit neural activity.
B. Optogenetics currently uses viral vectors to introduce the genes encoding the light-gated channels into the neurons of interest. This approach can be potentially problematic, as insertion of this engineered DNA at off-target sites in the genome could cause mutations that would alter or destroy the activity of critical genes. In addition, the stimulation of neurons by optogenetics requires a light source. In the case of a human patient, this would mean inserting a fiberoptic light source into the region of the brain that contains the foreign channels. This would represent a highly experimental treatment, henceit is currently only used in animal models to explore circuitry we do not yet fully understand.