[Optogenetic analysis of striatal circuits].

The striatum receives inputs from both cortical and subcortical structures, reflecting the role of the striatum as a limbic-motor interface. The relative simplicity of the cellular architecture of the striatum belies the complexity of the circuitry. Because synaptic inputs are intermingled, using classical methods to selectively activate or inhibit known populations of neurons has not been possible. The advent of optogenetics has enabled population-selective activation or inhibition in intact animals. In this review, I describe how optogenetic analysis can be used to study striatal circuits. First, I briefly introduce optogenetics and the widely used channelrhodopsin for excitation and halorhodopsin for inhibition. Next, I categorize optogenetic studies based on the approaches optogenetics have made possible, specifically (1) selective activation of identified synaptic inputs, (2) activation of convergent inputs to identify weak synaptic connections, (3) selective activation of identified neuronal populations in freely moving animals, and (4) cell identification for in vivo recording, and I discuss new insights into striatal circuits. Optogenetic approaches made impossible experiments possible and help to resolve the function of intact brain circuitry.