27 January 2011
Washington, DC USA
Scientists at the University of Pittsburgh have recorded neuron activity in adolescent rat brains that could reveal the biological root of the teenage propensity to consider rewards over consequences.
It may also explain why adolescents are more vulnerable to drug addiction, behavioural disorders, and other psychological ills.
The team reports that electrode recordings of adult and adolescent brain–cell activity during the performance of a reward–driven task show that adolescent brains react to rewards with far greater excitement than adult brains.
This frenzy of stimulation occurred with varying intensity throughout the study along with a greater degree of disorganisation in adolescent brains.
The brains of adult rats, on the other hand, processed their prizes with a consistent balance of excitation and inhibition.
Each row represents the activity in a neuron at key times during the task. At the time of reward, nearly one–third of adolescent neurons became excited (shown in red) though the level of inhibition (in blue) changed marginally. Adult neurons registered much higher inhibitory activity and less excitation.
The extreme difference in brain activity provides a possible physiological explanation as to why teenagers are more prone than adults to rash behavior, addiction, and mental diseases, said lead researcher Bita Moghaddam, a professor of neuroscience in Pitt's School of Arts and Sciences.
She and coauthor David Sturman, a Pitt neuroscience doctoral student, observed the disparate reactions to reward in individual neurons in the orbitofrontal cortex, a brain region that weighs payoff and punishment to plan and make decisions.
"The disorganised and excess excitatory activity we saw in this part of the brain means that reward and other stimuli are processed differently by adolescents," Moghaddam said.
"This could intensify the effect of reward on decision making and answer several questions regarding adolescent behavior, from their greater susceptibility to substance abuse to their more extreme reactions to pleasurable and upsetting experiences."
In addition, malfunctions in the orbitofrontal cortex have been observed in cases of schizophrenia, mood disorders, and other psychological disturbances, Moghaddam said.
The type of erratic activity in the cortex that she and Sturman observed could aggravate these conditions at a time when the maturing brain is vulnerable.
The study appears in the Journal of Neuroscience.
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