New Light Cascades deep into the World of Neuroscience

The brain....misunderstood, yet we struggle to understand. A typical mode of studying the brain has involved looking at brain waves that occur once a stimuli is introduced to a subject. Various psychology and neuroscience studies have used this approach of neuroimaging, however, being an imprecise study, direct and specific conclusions about brain function cannot be drawn. Scientists guess as to what this data may specifically mean or not mean based on what area of the brain these waves are occurring.

Further specific studies have come along, where fluorescent dyes are used to visualize a given pathway. For instance, some dyes react to specific atoms or ions, so the action of voltage gated calcium channels can be visualized. When calcium is released into the cell this leads to the release of a neurotransmitter. This can be visualized by the activated dye due to the influx of calcium into the cell. These approaches provide information, but the clear signal transduction still remains a mystery. One cannot see the actual signal flowing through the neuron, rather one doesn't necessarily know exactly which cells are communicating since the dye stains all cells regardless of what type they are...dopaminergic or otherwise.

Therefore, optogenetics breaks through this barrier as it serves a specific purpose. What about using genetics? Certain genes are turned on or off in a cell due to its specific cell type. A dopaminergic neuron has all the genes pertaining to the production of dopamine turned on. So, if one links this dopaminergic gene to a gene that encodes a dye, the dye will only be present in cells where this dopaminergic gene is turned on. Furthermore, this process allows for observation of a living organism in a natural environment where there are no forced stimuli (in contrast to earlier studies). A great idea, but what if we could go further?

What if we could control when these dyes, or indicators if you will, were turned on? Gero Miesenbock along with his postdoc fellow Boris Zemelman tackled this problem. Termed "actuators" these gene mechanisms consist of a light-activiated protein rhodopsin which reacts to light. So now, not only is the dye-encoding gene linked to the dopaminergic gene, the rhodopsin gene is linked as well. And when light is introduced, the rhodopsin activates the nerve through an electrical signal (which in a dopaminergic neuron leads to the release of dopamine). This is then visualized by the indicators which are engineered to only be present in the dopaminergic cells. Therefore, one can activate only the dopaminergic neurons by light, and visualize the result. CRAZY!!!!!!!!!!!!!!1