How are the neural processes for deciding when to move similar to and different from those for deciding what or how to move?

An awake person moves all the time. All these movements are characterized by different temporal and spatial patterns, often complex and influenced by both internal drive and external stimuli. This chapter reviews a series of classic neurophysiological experiments aimed at disentangling the neural activity underpinning the specific features of simple movements: when, what, and how. Neural activity can be assessed with fMRI or EEG. In “when” experiments, the subject can freely decide when to perform a specified movement. In “what” experiments, the subject must choose between different simple movements at a specific time. In “how” experiments, the subject must decide how to execute a complex action.