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Until now, no tools existed to selectively manipulate the small number of sparsely distributed neurons activated during a drug-related learned behavior. Here the authors describe a new method for selectively inactivating only those neurons activated by cocaine in an environment repeatedly paired with drug injections.
The mosaic analysis with repressible cell markers (MARCM) technique allows for lineage tracing in Drosophila. Here, the authors report an improvement on this technique, twin-spot MARCM, which permits high-resolution lineage tracing of both sister clones.
Transgenic expression of microbial channelrhodopsins in neurons allows direct light activation of ionic currents. Here, the authors describe a modified channelrhodopsin that remains open for seconds once it is activated by light and can be 'switched off' by a second light flash, thereby obviating the need for constant illumination during an experiment.