Genetic methods for illuminating the function of neural circuits.

Guided by the notion that biology itself offers some of the most incisive tools for studying biological systems, neurophysiologists rely increasingly on cell biological mechanisms and materials encoded in DNA to visualize and control the activity of neurons in functional circuits. Optical reporter proteins can broadcast the operational states of genetically designated cells and synapses; remote-controlled effectors can suppress or induce electrical activity. Many challenges, however, remain. These include the development of novel gene expression systems that target reporters and effectors to functionally relevant neuronal ensembles, the capacity to monitor and manipulate multiple populations of neurons in parallel, the ability to observe and elicit precisely timed action potentials, and the power to communicate with genetically designated target neurons through electromagnetic signals other than light.