Scientists in many different fields have been attracted to the study of habits because of the power habits have over behavior and because they invoke a dichotomy between the conscious, voluntary control over behavior, considered the essence of higher-order deliberative behavioral control, and lower-order behavioral control that is scarcely available to consciousness. A broad spectrum of behavioral routines and rituals can become habitual and stereotyped through learning. Others have a strong innate basis. Repetitive behaviors can also appear as cardinal symptoms in a broad range of neurological and neuropsychiatric illness and in addictive states. This review suggests that many of these behaviors could emerge as a result of experience-dependent plasticity in basal ganglia–based circuits that can influence not only overt behaviors but also cognitive activity. Culturally based rituals may reflect privileged interactions between the basal ganglia and cortically based circuits that influence social, emotional, and action functions of the brain.

Cyclic voltammetry reveals an extended mode of reward-predictive dopamine signalling in the striatum as rats navigate; signals increase as the rats approach distant rewards, instead of showing phasic or steady tonic activity, and the increases scale flexibly with the distance and size of the rewards. It has been suggested that when animals perform simple stimulus–response tasks, the phasic activity observed the in dopaminergic midbrain represents an expectation of immediately upcoming rewards. Ann Graybiel and colleagues now demonstrate a different form of reward-related dopamine signalling in the striatum. Using cyclic voltammetry, they observe prolonged dopamine signals in animals navigating mazes to obtain rewards. These responses steadily ramp up as animals approach their goals, and scale with both the distance and size of the rewards. These signals may represent motivational drive, and provide insight into the role of dopamine during extended goal-directed actions. Predictions about future rewarding events have a powerful influence on behaviour. The phasic spike activity of dopamine-containing neurons, and corresponding dopamine transients in the striatum, are thought to underlie these predictions, encoding positive and negative reward prediction errors1,2,3,4,5. However, many behaviours are directed towards distant goals, for which transient signals may fail to provide sustained drive. Here we report an extended mode of reward-predictive dopamine signalling in the striatum that emerged as rats moved towards distant goals. These dopamine signals, which were detected with fast-scan cyclic voltammetry (FSCV), gradually increased or—in rare instances—decreased as the animals navigated mazes to reach remote rewards, rather than having phasic or steady tonic profiles. These dopamine increases (ramps) scaled flexibly with both the distance and size of the rewards. During learning, these dopamine signals showed spatial preferences for goals in different locations and readily changed in magnitude to reflect changing values of the distant rewards. Such prolonged dopamine signalling could provide sustained motivational drive, a control mechanism that may be important for normal behaviour and that can be impaired in a range of neurologic and neuropsychiatric disorders.

Significance: Studies of beta oscillations, highlighted clinically because of exaggerated beta-band activity in Parkinson’s disease, have focused on measures averaged over multiple trials, and readers outside the field could have the misperception that beta oscillations persist over seconds. We show that brief bursts of oscillation are responsible for virtually all beta-band activity in healthy monkeys. The state called “beta synchronization” consists of numerous brief (∼40–120 ms) bouts of oscillation within a nonoscillatory background, and these bouts can also occur during periods of “desynchronization.” Thus, postmovement “synchronization” of beta represents a transient increase in oscillation probability, with different time courses in the motor cortex and striatum. We suggest that the timing and duration of these bursts are critical parameters for network function.