Figure 1.

Phasic dopamine signaling in the NAcc associated with drug seeking and taking (a) Phasic dopamine signaling consists of multiple phasic events (triangles). The first event is elicited by the animal’s approach of the operant lever (pre-response signal; 1), whereas a bigger second event is associated with the onset of the audiovisual cue (dark gray bar) that is presented in response to the lever press (post-response signal; 2). A set of peaks (3) that is observed with an onset of approximately 10 seconds after the lever press and the beginning of the drug infusion (light gray bar), is thought to be a direct consequence of the pharmacological effect of the drug. The latency of this pharmacological effect relative to the operant response appears to be more variable than for the post-response signal. (b) During extinction, the audiovisual stimulus presented after the lever press is not accompanied by a drug infusion. As a consequence, the post-response dopamine signal becomes smaller with repeated non-reinforced responding. In contrast, the pre-response signal remains relatively stable during extinction. This suggests that the pre-response signal reflects the motivation to obtain drug, whereas the post-response encodes the expectation of the drug infusion.