The prefrontal cortex, a brain area critical for executive functioning, has not reached its fully mature state yet in adolescence. Impulsivity, poor decision-making, sensation seeking are hallmarks of adolescent behavior (2/10)

It has been well known that improvement of cognitive performance in adolescence coincides with a number of structural changes in the brain, including volume and surface of the prefrontal cortex and maturation of white matter tracts (3/10)

However the brain alterations responsible for the changes in neural firing rate, which is ultimately altering the maturing cognitive functions, have remained elusive (4/10)

Tracking monkeys from late childhood to adulthood, we combined behavior, MRI, and single-neuron recordings. Our overarching result was that working memory improved as frontal lobe structural connectivity strengthened (5/10)

Prefrontal neuron firing rate generally increased through adolescence, while variability declined, and dimensionality of responses increased, supporting flexible coding and distractor resistance (6/10)

Unlike prior emphasis on gray matter thinning (e.g. due to pruning of unwanted synapses), our study shows cortical volume & thickness poorly predict cognitive maturation. White matter maturation was the key driver (7/10)

Long-distance tracts, including the superior fronto-occipital fasciculus and anterior cingulum, best predicted working memory precision and speed (8/10)

Because rhesus macaque brain development parallels human trajectories, these findings illuminate mechanisms of adolescent cognition and why connectivity disruptions may underlie psychiatric risk (9/10)