Abstract : Spinal cord injuries, along with myopathies, strokes or amputations can lead to very severe conditions where motor commands cannot be executed as intended. To cope with these deficits, brain-machine interfaces have been developed. Most research groups working in this field have conceived interfaces that try to reconstruct a movement from neuronal activity in the brain. Here, we tackle the problem differently by conditioning one or a few neurons in the motor cortex of awake rats to control the speed of a one dimensional actuator by increasing or decreasing their firing rate. In this protocol, knowing the initial coding space of the conditioned neurons was not a prerequisite. We observed that most neurons' activity could be modulated through operant conditioning, and could control the position of a bottle with water reward in front of the animal in real-time and for several seconds. Moreover, during the learning period, the conditioned neurons exhibited special properties compared to other non-conditioned neurons, in terms of their firing rate variability, latency of response and strength of rate modulation. This is the first demonstration of an external device controlled in real-time by conditioned neurons that adjust their activity to constantly changing demands.