Have you heard about optogenetics yet? If not, you soon will. Optogenetics techniques are sweeping neuroscience research. Named as the Method of the Year in 2010 by Nature Methods, optogenetics techniques are becoming widespread.
The reason is clear: optogenetics offer the unprecedented ability to manipulate specific cells in real-time in freely behaving animals essentially by controlling a light switch. This allows for the dissection of intricate microcircuits that was previously impossible. Specific brain regions and neuronal types can be turned on and off at will. The effect on animal behavior of activation of a specific neuronal circuit can be observed immediately. This is an exciting and far-reaching opportunity to fine-tune functional and neuroanatomical knowledge.
The technology began as the result of long-time collaborations between Drs. Edward Boyden and Karl Deisseroth, among others (Boyden 2011). To better define the roles of individual neurons, these pioneers sought a way to drive or silence specific neurons embedded in intact brain circuitry. They found the way using an ion channel expressed in the green algaChlamydomonas reinhardtii: channelrhodopsin-2 (ChR-2). ChR-2 is a cation-selective ion channel that is directly light-gated. In green alga, ChR-2serves to direct the alga to or from a light source to facilitate photosynthesis (Sineshchekov et al., 2002). When inserted into neurons, ChR-2 mediates light-driven spiking (Boyden et al., 2005). Viral transfection was first used to successfully express ChR-2 in neurons in vivo, thus opening the field of optogenetics to animal models (Arenkiel et al., 2007).
For in vivo use, an optical fiber is implanted into the brain for either acute or chronic use. Once the light is turned on, the cells expressing ChR-2 will be activated as the channel depolarizes the cell. Alternately, halorhodopsin expression is used to hyperpolarize a cell upon illumination, thus inactivating it at will (Tye and Deisseroth, 2012). In many cases, this will shorten the time frame required for behavioral experiments, as intervention with optogenetics requires no “wash-out” period, as pharmacological manipulations would (Tye and Deisseroth, 2012)… View Original Article»