Muñoz, W. et al. Cell Rep. 9, 2304–2316 (2014).

In studies of sparse neuronal subtypes, visual targeting of the genetically labeled neurons is an efficient way to obtain recordings of electrical activity, but this strategy is amenable to only those neurons in superficial brain layers. Muñoz et al. developed a method to target specific neurons in deeper brain layers with high efficiency. The researchers express the optogenetic actuator channelrhodopsin 2 in the neuronal subset of interest and randomly target neurons with a recording pipette. Once they approach a neuron, they deliver blue light via an optical fiber within the recording pipette. Evoked activity signifies that the researchers have targeted a neuron of interest, whereas they can quickly move on to another neuron if they do not observe any optogenetically induced activity.