Long-term stability of neural activity in the motor system

How established behaviors are retained and stably produced by a nervous system in constant flux remains a mystery. One possible solution is to fix the activity patterns of single neurons in the relevant circuits. Alternatively, activity in these circuits could change over time, provided that the network dynamics are contained within a manifold that produces stable behavior. To arbitrate between these possibilities, we recorded single unit activity in motor cortex and striatum continuously for several months as rats performed stereotyped motor behaviors - both learned and innate. We found long-term stability in behaviorally locked single neuron activity patterns across both brain regions. A small amount of neural drift observed over weeks of recording could be explained by concomitant changes in task-irrelevant behavioral output and the stochasticity of neural firing. These results suggest that stereotyped behaviors are stored and generated in stable neural circuits.