The neurobiology of adolescence: changes in brain architecture, functional dynamics, and behavioral tendencies.

A) Schematic of the behavioral task. Rats performed an instrumental behavior inside of a standard operant chamber. Each trial began with the onset of a cue light within a nose-poke hole (Cue). If the rat poked into that hole while the light was on (Poke) the light turned off and a food pellet was delivered to a food trough on the opposite wall. Once the animal poked into the food trough to retrieve the pellet (Pellet) a 5 sec inter-trial interval (ITI) was triggered, followed by the next trial. Rats could perform a maximum of 100 trials within a 30 min session. B) Adolescent and adult unit firing-rate activity during pellet retrieval after learning the task. Each graph is the activity of a representative adolescent or adult unit. Raster plots, which indicate the timing of spikes for each trial (row) are displayed above peri-event time histograms which average across trials in 50 ms bins. Units that were significantly activated (upper plots) or inhibited (lower plots), relative to a baseline period, are shown around the time of reinforcement. To the right of each plot is the proportion and percentage of units classified with the corresponding response pattern in a 500-ms window centered at pellet retrieval. As indicated, adolescents had substantially larger proportions of units that were activated during this period. Conversely, adults had a larger proportion of inhibited units. These age-related proportional differences were statistically significant (Chi-square test, p < 0.01). Adapted from Sturman and Moghaddam (2011).