A key limitation of previous attempts to explain basal ganglia function is their inadequate description of behavior. Behavior is often assumed to be the output of the nervous system, but this assumption is false. Repeating muscle output patterns does not repeat behavior. Rather, variable outputs must be generated to achieve consistent behavior. In biological systems, this is achieved using closed-loop negative feedback control, which has counterintuitive properties that are often misunderstood. Behavior is not the product of sensorimotor transformations, but the outward manifestation of closed-loop control, which is characterized by circular causation. The nervous system consists of a collection of hierarchically organized control systems that control a wide variety of input variables. The neural signal, measured as the rate of firing, is an analog signal used in control systems. The control hierarchy uses analog signaling to represent specific variables, and neural circuits implement the basic analog computations. Current thinking on neural signaling is influenced by information theory and digital computing, which offer misleading analogies.