An optical brain

Green algae use a light-activated ion channel to control phototaxis. Now, Edward Boyden, Feng Zhang, Karl Deisseroth (Stanford University, Stanford, CA), and colleagues have used the same channel to control the rapid spiking activity of neurons.

Experimental control of neural activity has become more and more sophisticated, with glutamate uncaging and multineuron patch clamping allowing the targeting of a specific neural area. But there is a catch. “You can't target cell types in that way,” says Deisseroth. Usually the individual cell types “are sparsely embedded in the networks.”

The obvious solution to this is genetics. Promoters to drive expression in specific cell types are available, as many of the interneuron types express unique neuropeptides or other markers. Initial attempts have met with partial success, but the complexity of the introduced signal cascades has meant that control...