Reduced neuronal inhibition and coordination of adolescent prefrontal cortex during motivated behavior.

Adolescence is a time of both cognitive maturation and vulnerability to several major psychiatric illnesses and drug dependence. There is increasing awareness that behavioral or pharmacological intervention during this period may be critical for disease prevention in susceptible individuals. Therefore, we must attain a deeper understanding of how the adolescent brain processes salient events relevant to motivated behavior. To do this, we recorded single-unit and local field potential activity in the orbitofrontal cortex of rats as they performed a simple reward-driven operant task. Adolescents encoded basic elements of the task differently than adults, indicating that neuronal processing of salient events differs in the two age groups. Entrainment of local field potential oscillations, variance in spike timing, and relative proportions of inhibitory and excitatory responses differed in an event-specific manner. Overall adolescent phasic neural activity was less inhibited and more variable through much of the task. Cortical inhibition is essential for efficient communication between neuronal groups, and reduced inhibitory control of cortical activity has been implicated in schizophrenia and other disorders. Thus, these results suggest that reduced inhibitory responses of adolescent cortical neurons to salient events could be a critical mechanism for some of the increased vulnerabilities of this period.