Neural circuits display complex spatiotemporal patterns of activity on the millisecond timescale during behavior. Understanding how these activity patterns drive behavior is a fundamental problem in neuroscience, and remains a major challenge due to the complexity of their spatiotemporal dynamics. I will describe a strategy for "all-optical" simultaneous imaging and manipulation of patterns of activity in neural circuits in vivo with single-spike and single-neuron precision. This approach should open up new experiments for probing the nature of the neural code during behaviour.

[1] Packer et al. Nature Methods 12: 140-6 (2015).