Figure 3.

The effect of increasing price, shown as ratio requirement, on the number of operant pellets consumed in rats with accumbens dopamine depletions compared to rats in the vehicle control group. These results are based on data from Aberman and Salamone (1999) . The data are represented as a demand curve, calculated from the mean number of reinforcement pellets consumed (shown on a log scale) as a function of price (ratio requirement). Although comparable levels of consumption in dopamine (DA)-depleted and control groups were seen with the FR1 schedule, dopamine-depleted rats showed markedly reduced consumption relative to the control group at higher ratio levels.