Pisanello, F. et al. Neuron 82, 1245–1254 (2014).

To unravel the function of different brain subregions in a neural circuit, spatially selective and user-defined optogenetic control over these subregions is desirable. To achieve this goal, Pisanello et al. developed multipoint-emitting optical fibers. The tapered ends of these fibers are gold coated, with the exception of some small windows along the tip of the fiber. The researchers directed light emission to different windows by capitalizing on the behavior of light at reflective surfaces and by simply changing the input angle of a laser beam into the optical fiber. In the mouse striatum or cortex, the optogenetic activation of GABAergic neurons in different subregions led to the activation of different populations of neurons. This tool provides a versatile option for optically manipulating neural circuits.