Targeted stimulation of motor cortex ensembles drives learned movements.

Stimulating about 20 layer 2/3 motor cortex neurons whose activity precedes movement onset triggered lever-press-like movements in task-engaged mice and reproduced the learned population activity pattern. Trial-by-trial variability in the evoked activity and movements was predicted by the initial state of M1 before stimulation. Stimulating movement-following neurons, or stimulating in disengaged mice, failed, supporting a causal, active role for M1 in generating learned movements.