Strong Gamma Frequency Oscillations in the Adolescent Prefrontal Cortex.

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Cognitive Neuroscience

Background:

• Working memory matures into adulthood in humans and primates.
• Adolescent development shows increased single-neuron firing rates in the prefrontal cortex.
• Less is known about how coordinated neuronal activity, reflected in local field potentials (LFPs), changes during development.

Purpose of the Study:

• To investigate the effects of adolescent development on LFP activity during a working memory task.
• To understand how coordinated neural network activity in the prefrontal cortex matures.

Main Methods:

• Three male rhesus monkeys performed an oculomotor delayed response task at adolescent and adult stages.
• Simultaneous single-unit and LFP signals were recorded from the dorsolateral prefrontal cortex (areas 8a and 46).
• Analyzed power in the gamma frequency range (32-128 Hz) relative to baseline.

Main Results:

• Adolescent monkeys exhibited higher gamma power during cue and delay periods compared to adults.
• These developmental changes were independent of task performance.
• In adults, high-firing neurons were associated with increased gamma power; this association was not as strong in adolescents.
• Gamma power increase during the delay period was selective for neuronal sites encoding stimulus information.

Conclusions:

• Gamma power decrease is a characteristic of prefrontal cortex maturation.
• Adolescent prefrontal cortex shows stronger gamma power during working memory maintenance than expected.
• Findings suggest a refinement of information encoding during prefrontal cortex maturation and may inform our understanding of schizophrenia as a potential state of excessive prefrontal maturation.