Dopamine and inverse incentive learning

Dopamine and inverse incentive learning explains that dopamine determines an incentive–value continuum. Novel and intense stimuli innately produce rapid dopamine neurons activation followed by inhibition. The repeated presentation of novel stimuli leads to a loss of this effect. Aversive stimuli, biologically important by definition, often deactivate dopamine neurons and may produce inverse incentive learning, leading to conditioned inverse incentive stimuli with decreased ability to elicit approach and other responses. The offset of aversion may increase the firing of dopamine neurons producing incentive learning about safety-related stimuli. Habituation to stimuli enhances their ability to produce inverse incentive learning, suggesting that inverse incentive learning may occur during habituation. In the end, there may be no “neutral” stimuli, only stimuli that lie on a continuum of incentive value from strong conditioned incentive stimuli to strong conditioned inverse incentive stimuli with most of the things we encounter in day-to-day life falling in between.

Dopamine and the elements of incentive learning

Dopamine and the elements of incentive learning explains how, in lever pressing for food tasks, incentive learning produces a gradient of attractiveness of environment stimuli: during magazine training, food activates dopaminergic neurons and the click and food cup become conditioned incentive stimuli, acquiring the ability to elicit approach and other responses; during lever-press training, the click activates dopaminergic neurons and the lever and lever-related stimuli become conditioned incentive stimuli. In conditioned place preference, amphetamine enhances dopaminergic neurotransmission and stimuli paired with amphetamine become conditioned incentive stimuli. In conditioned activity experiments, test-box stimuli paired with a dopamine-enhancer, e.g., cocaine, produce greater activity revealing incentive learning. In conditioned avoidance, the offset of an aversive warning stimulus putatively activates dopaminergic neurons leading safety-related stimuli to become conditioned incentive stimuli. If trained animals are treated with a dopamine receptor blocker, the initially intact ability of conditioned incentive stimuli to control responding declines over trials.

Dopamine and reward-related learning

Dopamine and reward-related learning describes how the intellectual influence of behaviorism declined in the middle of the twentieth century as descriptions of behavioral phenomena that violated the putative laws of learning accumulated. Incentive theory along with an ethological perspective that emphasized animals’ specific behavioral adaptations for survival in their natural environment provided an alternative. Thus, rewarding stimuli produce incentive learning, the acquisition of neutral stimuli of an increased ability to elicit approach and other responses. The reward-related learning effects of food were shown to depend on dopamine and dopamine was implicated in avoidance learning. Results suggest that in untrained animals, tested while in a dopamine-depleted state, conditioned incentive stimuli fail to acquire the ability to elicit approach and other responses; in trained animals tested while in a dopamine-depleted state, conditioned incentive stimuli gradually lose their ability to elicit approach and other responses.