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

Abstract

Adolescence is a period of increased behavioral and psychiatric vulnerabilities. It is also a time of dramatic structural and functional neurodevelopment. In recent years studies have examined the precise nature of these brain and behavioral changes, and several hypotheses link them together. In this review we discuss this research and recent electrophysiological data from behaving rats that demonstrate reduced neuronal coordination and processing efficiency in adolescents. A more comprehensive understanding of these processes will further our knowledge of adolescent behavioral vulnerabilities and the pathophysiology of mental illnesses that manifest during this period.

Figure 1

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).