Instrumental training.

<p>Instrumental training on the active and inactive lever, shown as average lever presses over days displayed separately for the cocaine group (1A) and the vehicle group (1B). Means +/− SEM. *** = p<0.001.</p

Experimental timeline: Experiment 1.

<p>Experimental timeline: Experiment 1.</p

Cocaine sensitization in experiments 1 and 2.

<p>5A – Locomotor activity on days 1 and 6 for the cocaine and vehicle groups from experiment 2. 5B – Magazine entries during cocaine sensitization for the cocaine and vehicle groups from experiment 2, in which there was no pre-training before sensitization. 5C – Magazine entries during cocaine sensitization for the cocaine and vehicle groups from experiment 1, in which there was pre-training before sensitization. Means +/− SEM. * = p<0.05, ** = p<0.01.</p

Pavlovian-to-instrumental transfer test results.

<p>PIT test results, calculated as an elevation ratio for both lever presses (3A) and magazine entries (3B) for the cocaine and vehicle groups. The dashed line at 0.5 represents the baseline level of responding. Means +/− SEM. * = p<0.05, ** = p<0.01, *** = p<0.001.</p

Pavlovian training.

<p>Pavlovian training, shown as magazine entries made in response to the CS and in the 30 s period immediately before it (preCS), displayed separately for CS identity and group. CS+ trials for the cocaine group (2A) and the vehicle group (2C) are shown next to CS− trials for the cocaine group (2B) and vehicle group (2D). Means +/− SEM. ** = p<0.01.</p

Normalized within-session SCM consumption rates in Experiment 1.

<p>The large data points reflect group mean consumption rates in 2-min bins for adolescent males (top-left), adolescent females (top-right), adult males (bottom-left), and adult females (bottom-right). The small shaded data points within each panel represent data from individual rats within that group. The thick line is the best-fitting negative exponential function. The within-panel α and β values are the fitted values of the corresponding exponential function (i.e., α is the y-intercept and a metric for reward palatability; β is the function’s decay and a metric for the induction of satiety). Adolescent males exhibited significantly greater initial consumption rates (α) and decay rates (β) than each of the other three groups, <i>p</i>s < .003.</p

Linear mixed-effects model output for the analysis of normalized saccharin consumption rates in concentration curve testing in Experiment 2.

<p>Linear mixed-effects model output for the analysis of normalized saccharin consumption rates in concentration curve testing in Experiment 2.</p

Linear mixed-effects model output for the analysis of normalized SCM consumption in Experiment 1.

<p>Linear mixed-effects model output for the analysis of normalized SCM consumption in Experiment 1.</p

Nonlinear mixed-effects model output for the analysis of normalized SCM consumption rates in Experiment 1 and normalized saccharin consumption rates in training of Experiment 2.

<p>Nonlinear mixed-effects model output for the analysis of normalized SCM consumption rates in Experiment 1 and normalized saccharin consumption rates in training of Experiment 2.</p

Bivariate scatter plots of individual rats’ mean normalized SCM consumption, initial consumption rates (α), and consumption rate decay (β) in Experiment 1.

<p>Each data point represents an individual rat, identified with respect to its sex and age group. The solid and dotted lines are the best-fitting regression lines for each groups’ data. The thick dashed line represents the best-fitting regression line of the data collapsed across groups. There were significant positive relationships between α and β, <i>p</i> = .001 (left), and between α and mean normalized SCM intake (middle), <i>p</i> < .001. Note: The linear fits are extended beyond the range of the data points for ease of visual interpretation. Adol-M = adolescent-males; Adol-F = adolescent-females; Adult-M = adult-males; Adult-F = adult-females; (D) = data; (F) = linear fit.</p