Figure 1.
Average dopamine release in the NAc core of a rat at the presentation of a cue and reward after Pavlovian conditioning. The rat was trained for 7 days on a Pavlovian conditioning paradigm: each day it received 25 pairings of a cue (8-s lever extension and cue light illumination) and a reward (0.1 ml of Ensure® chocolate drink). On the eighth day, dopamine was recorded in the NAc core during an identical Pavlovian session. The figure illustrates the dopamine release associated with cue and reward presentation, signal-averaged across the 25 trials. The color plot shows the changes in current at each applied potential over a 16-s window; cue presentation (“C”) is at 4 s and reward delivery (“R”) is at 12 s. Current at the oxidation potential of dopamine (white dotted line) is depicted in the line trace above the color plot. The transients are confirmed to be dopaminergic by evaluation of the cyclic voltammograms (inset above). As previously reported (Day et al., 2007; Stuber et al., 2008), dopamine release is more robust to the cue than to the reward delivery after Pavlovian conditioning.