This paper discusses work on the function of the motor cortex as revealed by single cell recordings in monkeys and artificial neural network modelling. Our key conceptual approach both in behavioural neuroscience and neural network modeling of motor cortical function relies on reconstructing, visualizing, and modelling the activity in neuronal populations, indeed a key concept advanced by Hebb (1949). The behaviour investigated ranges from exertion of isometric force to pointing movements to complex cognitive processing. The functional properties of single cells with respect to the direction of movement in space are described as well as a population code which provides a unique measure for this direction. Finally, the results of modeling studies are discussed in which directional population activity is used as an input to an artificial neural network to drive a simulated arm.