This article reviews the neuronal activities related to reward processing in the primate orbitofrontal cortex (OFC), striatum, and midbrain dopamine neurons. OFC neurons showed three types of reward-related activity: responses to reward-predicting instructions, activations during the expectation period before reward, and responses following reward. These activities discriminated between different rewards based on the animals' preferences. Striatal neurons were also activated in relation to reward expectation and detection, and showed activities related to movement preparation and execution. Dopamine neurons responded to rewards and reward-predicting stimuli, coding an error in reward prediction. These structures showed multiple, heterogeneous activations related to specific aspects of rewards, which may represent the neuronal substrates of rewards during learning and established behavior. The OFC is crucial for motivational control of goal-directed behavior. Lesions in the OFC impair decision-making about action outcomes. Monkeys with OFC lesions respond abnormally to reward contingencies and show altered reward preferences. OFC neurons respond selectively to rewards or aversive stimuli and process reward preferences. The OFC is connected to the basal ganglia via fronto-striatal projections. Parkinsonism and chorea involve the striatum and substantia nigra, leading to deficits in voluntary behavior. Dopamine inputs to the striatum are involved in approach behavior, reward evaluation, reward-related learning, and the action of addictive substances. The study investigated the neuronal processing of reward information to understand the basis of voluntary, goal-directed behavior. Dopamine neurons responded to primary rewards and reward-predicting stimuli. The study compared neuronal activity in the OFC, striatum, and dopamine neurons during different reward conditions. The results showed that OFC neurons discriminated between different rewards, and striatal neurons showed activities related to movement preparation and execution. Dopamine neurons responded to rewards and reward-predicting stimuli, coding an error in reward prediction. The study found that OFC neurons showed three types of reward-related activity: responses to reward-predicting instructions, activations during the expectation period before reward, and responses following reward. These activities were related to the upcoming or past delivery of reward. Striatal neurons showed activities related to reward expectation and detection, and also to movement preparation and execution. Dopamine neurons were activated by unpredictable rewards and reward-predicting stimuli but were depressed by omitted rewards. The different forms of reward processing were found in different neuronal populations in the OFC and striatum, while dopamine neurons showed any of the three forms depending on the situations. The study found that OFC neurons showed a limited spectrum of covariations with behavioral events compared to other prefrontal cortex regions. OFC neurons coded motivational aspects of goal-directed behavior, influencing 'why' a behavioral reaction is performed. These activities may result from trans-synaptic inputs from the striatum and inputs from the amygdala and temporal lobe. The study also found that striatal neurons showed a large spectrum of other behavioral relationshipsThis article reviews the neuronal activities related to reward processing in the primate orbitofrontal cortex (OFC), striatum, and midbrain dopamine neurons. OFC neurons showed three types of reward-related activity: responses to reward-predicting instructions, activations during the expectation period before reward, and responses following reward. These activities discriminated between different rewards based on the animals' preferences. Striatal neurons were also activated in relation to reward expectation and detection, and showed activities related to movement preparation and execution. Dopamine neurons responded to rewards and reward-predicting stimuli, coding an error in reward prediction. These structures showed multiple, heterogeneous activations related to specific aspects of rewards, which may represent the neuronal substrates of rewards during learning and established behavior. The OFC is crucial for motivational control of goal-directed behavior. Lesions in the OFC impair decision-making about action outcomes. Monkeys with OFC lesions respond abnormally to reward contingencies and show altered reward preferences. OFC neurons respond selectively to rewards or aversive stimuli and process reward preferences. The OFC is connected to the basal ganglia via fronto-striatal projections. Parkinsonism and chorea involve the striatum and substantia nigra, leading to deficits in voluntary behavior. Dopamine inputs to the striatum are involved in approach behavior, reward evaluation, reward-related learning, and the action of addictive substances. The study investigated the neuronal processing of reward information to understand the basis of voluntary, goal-directed behavior. Dopamine neurons responded to primary rewards and reward-predicting stimuli. The study compared neuronal activity in the OFC, striatum, and dopamine neurons during different reward conditions. The results showed that OFC neurons discriminated between different rewards, and striatal neurons showed activities related to movement preparation and execution. Dopamine neurons responded to rewards and reward-predicting stimuli, coding an error in reward prediction. The study found that OFC neurons showed three types of reward-related activity: responses to reward-predicting instructions, activations during the expectation period before reward, and responses following reward. These activities were related to the upcoming or past delivery of reward. Striatal neurons showed activities related to reward expectation and detection, and also to movement preparation and execution. Dopamine neurons were activated by unpredictable rewards and reward-predicting stimuli but were depressed by omitted rewards. The different forms of reward processing were found in different neuronal populations in the OFC and striatum, while dopamine neurons showed any of the three forms depending on the situations. The study found that OFC neurons showed a limited spectrum of covariations with behavioral events compared to other prefrontal cortex regions. OFC neurons coded motivational aspects of goal-directed behavior, influencing 'why' a behavioral reaction is performed. These activities may result from trans-synaptic inputs from the striatum and inputs from the amygdala and temporal lobe. The study also found that striatal neurons showed a large spectrum of other behavioral relationships