Neuron 242 Activation by Primary Rewarding Stimuli

[this issue of Neuron]). The structures included the do-pamine system, as many of the stimulation sites were in close proximity to axons of dopamine neurons or to amphetamine, and nicotine lead to increases in dopa-Cambridge CB2 3DY mine concentration in the ventral striatum and frontal United Kingdom cortex, which appears to be a crucial mechanism of drug addiction. In view of these well-established results, several studies investigated neuronal mechanisms of Recent neurophysiological studies reveal that neurons reward by studying the impulse activity of single neurons in certain brain structures carry specific signals about in the dopamine system and other presumptive reward past and future rewards. Dopamine neurons display structures. In particular, we were interested to under-a short-latency, phasic reward signal indicating the stand which specific information about rewards would difference between actual and predicted rewards. The be coded by the different neuronal systems. signal is useful for enhancing neuronal processing and The present review comprises seven sections which learning behavioral reactions. It is distinctly different (1) summarize the basic neurophysiological results ob-from dopamine's tonic enabling of numerous behav-tained from dopamine neurons; (2) interpret these re-ioral processes. Neurons in the striatum, frontal cor-sults in relation to formal issues of animal learning the-tex, and amygdala also process reward information ory; (3) make a case for different functions depending but provide more differentiated information for identi-on the time courses of dopamine fluctuations and com-fying and anticipating rewards and organizing goal-pare the reward processing with other functions of do-directed behavior. The different reward signals have pamine systems; (4) assess how the dopamine reward complementary functions, and the optimal use of re-signal influences postsynaptic structures to mediate the wards in voluntary behavior would benefit from inter-known behavioral functions of reward; (5) compare the actions between the signals. Addictive psychostimu-reward coding of dopamine neurons with other brain lant drugs may exert their action by amplifying the structures and discuss how neurons might use the re-dopamine reward signal. ward information for controlling goal-directed behavior, decision-making, and intentional behavior; (6) suggest Introduction hypotheses on how addictive drugs might abuse the The discovery of neurons synthesizing and releasing the dopamine reward signal; and (7) provide an outlook on neurotransmitter dopamine in the brain has prompted future experiments on dopamine and reward. a number of interesting proposals concerning their function. Following such far-fetched suggestions as an Basic Results involvement in regulating blood pressure, more recent Cell bodies of dopamine neurons …