Flexible control of population spike rate through multiphoton optogenetics

Sensory perceptions entail the activation of thousands of interrelated neurons, each of these neurons can fire at distinct rates at different times. Despite this vast ‘activity space’ not all possible combinations of activity happen – instead lower dimensional subspaces define what are valid or invalid patterns. However, even the most advanced manipulation approaches so far are incapable of recreating a specific multi-neuron pattern. Here we describe a new approach based on holographic multiphoton optogenetics that allows us to write the numerically correct number of action potentials into a group of neurons, allowing us to write directly and flexibly to activity space.