Timescales of myelin maturation in the human prefrontal cortical ribbon

​​The human cerebral cortex undergoes protracted and asynchronous postnatal myelination that extends throughout adolescence and helps to refine ongoing circuit plasticity. Histological and neuroimaging studies have shown that the human cortex does not myelinate synchronously; rather, sensorimotor cortex myelinates early and the prefrontal cortex (PFC) myelinates late. However, when myelin matures across PFC cortical layers—which differ in their connectivity targets, neurobiological features, and functional roles—is not clear, precluding insight into the maturation of layer-stratified cognitive processing hierarchies. This talk will explore findings obtained using 7 Tesla relaxometry data collected longitudinally from adolescents and young adults (ages 10 to 32 years) to chart myelin maturation across deep and superficial layers of the frontal cortex and link myelination to neurocognitive specialization. The talk will first present evidence from intracortical depth profiling of a deep-to-superficial axis of myelin maturational timing in the frontal cortical ribbon. Next, the talk will describe results obtained when integrating cortical myelin imaging with EEG, which link higher myelin in deeper layers of the lateral PFC to a faster timescale of dynamical changes in neural activity. Finally, the talk will highlight data relating myelin in deep and superficial PFC to higher learning rates and faster cognitive, but not sensorimotor, processing speed. Talk attendees will gain an appreciation for how divergent maturational timing in deep and superficial layers may be a mechanism through which late-developing association cortex balances cognitively-relevant increases in circuit stability with extended neuroplasticity.