​​​​​​​Talk from Robert Turner – Max Planck Institute for Human Cognitive and Brain Sciences

A​bstract:​

Histological studies of myelin-stained sectioned cadaver brain and in-vivo myelin-weighted magnetic resonance imaging show that the cerebral cortex is organized into cortical areas with generally well-defined boundaries, which have consistent internal patterns of myelination—their myeloarchitecture. Cortical myelinated axons can be classified into radialaxons, mostly connecting excitatory pyramidal neurons to other neurons via the white matter, and tangential neurons providing intracortical connections. Recent histological studies show that many of these tangential myelinated axons arise from interneurons that stain for parvalbumin, identifying them as inhibitoryneurons. Further recent discoveries have revealed that the process of myelination is largely driven in development by neural experience, such thatthe axonal passage of action potentials increases axonal diameter and stimulatesneighbouring oligodendrocytes to perform their task of wrapping axons with myelin. This bootstrapping process, in which the traffic of action potentialsfacilitates increased traffic, suggests the hypothesis that themyeloarchitecture in each cortical area reveals the principal corticalmicrocircuits required for the function of that area, fine-tuned by experience.If this idea is correct, observation using high resolution quantitative MRI of the sequential maturation of specific brain areas throughout the lifespan, combinedwith unsmoothed fMRI data and dMRI tractography, can provide evidence for neuropsychological models of the stages of normal and abnormal cognitive development. Such an approach may provide objective biomarkers for the identification of different types of mental illness.​